Laser irradiation method and method of manufacturing a semiconductor device

ABSTRACT

A method of manufacturing a semiconductor device is provided which uses a laser crystallization method capable of increasing substrate processing efficiency. An island-like semiconductor film including one or more islands is formed by patterning (sub-island). The sub-island is then irradiated with laser light to improve its crystallinity, and thereafter patterned to form an island. From pattern information of a sub-island, a laser light scanning path on a substrate is determined such that at least the sub-island is irradiated with laser light. In other words, the present invention runs laser light so as to obtain at least the minimum degree of crystallization of a portion that has to be crystallized, instead of irradiating the entire substrate with laser light.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a laser irradiation method forcrystallizing a semiconductor film using a laser light or for performingactivation after ion implantation and to a method of manufacturing asemiconductor device.

[0003] 2. Description of the Related Art

[0004] In recent years, a technique of forming a TFT on a substrate hasgreatly progressed, and its application and development for activematrix semiconductor display devices have been advanced. In particular,since a TFT using a polycrystalline semiconductor film has higherfield-effect mobility (also referred to as mobility) than a TFT using aconventional amorphous semiconductor film, it enables high-speedoperation. Although the pixel is conventionally controlled by a drivingcircuit provided outside the substrate, it is therefore possible tocontrol the pixel by the driving circuit formed on the same substratewhere the pixel is formed.

[0005] Incidentally, as for the substrate used in the semiconductordevice, a glass substrate is regarded as promising in comparison with asingle crystal silicon substrate in terms of the cost. A glass substrateis inferior in heat resistance and is easily subjected to thermaldeformation. Therefore, in the case where a polysilicon TFT is formed onthe glass substrate, in order to avoid thermal deformation of the glasssubstrate, the use of laser annealing for crystallization of thesemiconductor film is extremely effective.

[0006] Characteristics of laser annealing are as follows: it can greatlyreduce a processing time in comparison with an annealing method usingradiation heating or conductive heating; and it hardly causes thermaldamage to the substrate by selectively and locally heating asemiconductor or the semiconductor film, for example.

[0007] Note that the laser annealing method here indicates a techniqueof re-crystallizing the damaged layer formed on the semiconductorsubstrate or the semiconductor film, and a technique of crystallizingthe semiconductor film formed on the substrate. Also, the laserannealing method here includes a technique applied to leveling orsurface reforming of the semiconductor substrate or the semiconductorfilm. A laser oscillation apparatus applied thereto is a gas laseroscillation apparatus represented by an excimer laser or a solid laseroscillation apparatus represented by a YAG laser. It is known that theapparatus performs crystallization by heating a surface layer of thesemiconductor by irradiation of the laser light in an extremely shortperiod of time of about several tens of nanoseconds to several tens ofmicroseconds.

[0008] Lasers are roughly divided into two types: pulse oscillation andcontinuous oscillation, according to an oscillation method. In the pulseoscillation laser, an output energy is relatively high, so that massproductivity can be increased by setting the size of a beam spot toseveral cm² or more. In particular, when the shape of the beam spot isprocessed using an optical system and made to be a linear shape of 10 cmor more in length, it is possible to efficiently perform irradiation ofthe laser light to the substrate and further enhance the massproductivity. Thus, for crystallization of the semiconductor film, theuse of a pulse oscillation laser is becoming mainstream.

[0009] However, in recent years, in crystallization of the semiconductorfilm, it is found that grain size of the crystal formed in thesemiconductor film is larger in the case where the continuous wave laseris used than the case where the pulse oscillation laser is used. Whenthe crystal grain size in the semiconductor film becomes large, themobility of the TFT formed using the semiconductor film becomes high.For this reason, a continuous wave laser has been attracting attentionrecently.

[0010] However, since the maximum output energy of the continuous wavelaser is generally small in comparison with that of the pulseoscillation laser, the size of the beam spot is as small as about 10⁻³mm². Accordingly, in order to perform processing on one large substrate,it is necessary to move a beam irradiation position on the substrateupward and downward, and right and left, and the processing time persubstrate is prolonged. As a result, the efficiency of substrateprocessing is poor and there is an important problem of how to improvethe processing speed of the substrate.

[0011] Note that beam spot length adjustment technologies using a slithave conventionally been used (refer to, for example, Patent Document 1and Patent Document 2 below).

[0012] Further, technologies using a laser light of continuousoscillation for crystallization after forming the semiconductor filminto an island shape have conventionally been used (refer to, forexample Non-Patent Document 1 below).

[0013] (Patent Document 1)

[0014] JP 11-354463 A (page 3, FIG. 3)

[0015] (Patent Document 2)

[0016] JP 09-270393 A (pages 3 to 4, FIG. 2)

[0017] (Non-Patent Document 1)

[0018] Akito Hara, Yasuyoshi Mishima, Tatsuya Kakehi, Fumiyo Takeuchi,Michiko Takei, Kenichi Yoshino, Katsuyuki Suga, Mitsuru Chida, and NobuoSasaki, Fujitsu Laboratories Ltd., “High Performance Poly-Si TFTs on aGlass by a Stable Scanning CW Laser Lateral Crystallization”, IEDM2001.

SUMMARY OF THE INVENTION

[0019] The present invention has been made in view of the above problem,and an object of the present invention is therefore to provide a laserirradiation method using a laser crystallization method that can raisethe substrate processing efficiency and mobility of a semiconductor filmfrom those of prior art and to provide a method of manufacturing asemiconductor device which uses the laser irradiation method.

[0020] The present invention uses shape data (pattern information) of amask of a semiconductor film to grasp which part of the semiconductorfilm becomes an island-like semiconductor film (island). Then, anisland-like semiconductor film that includes one or more of such islandsis formed by patterning (sub-island). The sub-island is improved incrystallinity by laser light irradiation, and then patterned to form anisland.

[0021] Furthermore, the present invention uses pattern information of asub-island to determine a laser light scanning path on a substrate sothat at least the sub-island is irradiated with laser light. In otherwords, the present invention runs laser light so as to obtain at leastthe minimum degree of crystallization of a portion that has to becrystallized, instead of irradiating the entire substrate with laserlight. With the above structure, time for laser irradiation of otherportions than a sub-island can be saved to shorten the whole laserirradiation time and improve the substrate processing speed. The abovestructure also makes it possible to avoid damage to a substrate which iscaused by irradiating a portion that does not need laser irradiationwith laser light.

[0022] In the present invention, a marker may be formed in advance on asubstrate by laser light or the like, or a marker and a sub-island maybe formed at the same time. By forming a marker and a sub-islandsimultaneously, one less marker mask is needed and the marker can bepositioned more accurately than when forming it by laser light tothereby improve the positioning accuracy. The present invention uses themarker as the reference and determines the laser light scanning positionbased on pattern information of the sub-island.

[0023] The present invention sets intentionally the laser light scanningdirection such that, as the beam spot reaches a sub-island while thesubstrate is scanned with laser light, one point of the beam spot comesinto contact with the sub-island viewed from the direction perpendicularto the substrate. For example, if a sub-island has a polygonal shapewhen viewed from above the substrate, laser light first runs in a mannerthat brings the beam spot into contact with one corner of thesub-island. If a part or the entire length of a sub-island is curvedwhen viewed from above the substrate, the laser light scanning directionis determined such that one point of the beam spot comes into contactwith the curved portion of the sub-island first. Laser light irradiationis started from the one contact point to commence growth of crystalshaving <100> orientation from the contact point and the vicinitythereof. The laser light scanning is continued until irradiation of thesub-island with laser light is finished. As a result, the <100>orientation ratio of the entire sub-island is improved.

[0024] When an island with a high <100> orientation ratio is used for anactive layer of a TFT, the TFT can have high mobility. An active layerhaving a high <100> orientation ratio can reduce fluctuation in filmquality of a gate insulating film formed thereon and accordingly canreduce fluctuation in TFT threshold voltage.

[0025] When a sub-island is irradiated with laser light, microcrystalsare undesirably formed in the vicinity of edges of the sub-island viewedfrom above the substrate. For instance, a large number of microcrystalshaving a grain size of less than 0.1 μm are found in the vicinity ofedges of a sub-island irradiated with a pulse oscillation excimer laserlight, although it depends on the thickness of a semiconductor film, andthe grain sizes of the microcrystals are smaller than the grain sizes ofcrystals formed in the center of the sub-island. This is supposedlybecause heat by laser light diffuses to the substrate differently in thevicinity of edges and in the center.

[0026] Therefore, the present invention removes, after laser lightcrystallization, portions in the vicinity of edges that have poorcrystallinity by patterning and uses the center of the sub-island thathas better crystallinity to form an island. Which part of a sub-islandis to be removed by patterning to form an island can be appropriatelydetermined at designer's discretion. The crystallinity of an island canbe enhanced more by crystallizing a sub-island with laser light and thenforming an island in this way instead of directly crystallizing anisland with laser light.

[0027] Furthermore, the present invention uses a slit to cut off aportion of a beam spot that is low in energy density. The use of a slitallows a sub-island to receive irradiation by laser light of relativelyuniform laser energy density and the sub-island can be crystallizeduniformly. Providing a slit also makes it possible to change the widthof a part of a beam spot in accordance with pattern information of asub-island. This reduces restrictions in layout of a sub-island and anactive layer of a TFT as well. The beam spot width means the length of abeam spot in the direction perpendicular to the scanning direction.

[0028] Shapes of beam spots that can be used in the present inventioninclude an ellipse, a rectangle, a line, and others.

[0029] One beam spot obtained by synthesizing laser lights that areemitted from plural laser oscillation apparatuses may be used in lasercrystallization. This structure allows low energy density portions oflaser lights to compensate one another.

[0030] After a semiconductor film is formed, or after a sub-island isformed, the semiconductor film may be crystallized by laser lightirradiation without exposing the film to the air (rare gas, nitrogen,oxygen, or other specific gas atmosphere or a reduced pressureatmosphere is employed). This structure can prevent molecule-levelcontaminants in a clean room, such as boron contained in a filter forenhancing the cleanliness of air, from mixing in the semiconductor filmduring laser light crystallization.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the accompanying drawings:

[0032]FIGS. 1A to 1D are diagrams showing a laser irradiation method ofthe present invention;

[0033]FIGS. 2A to 2D are diagrams showing a shape and energy densitydistribution of a laser beam;

[0034]FIGS. 3A and 3B are diagrams showing the energy densitydistribution of a laser beam;

[0035]FIGS. 4A and 4B are diagrams showing the shape and energy densitydistribution of a laser beam;

[0036]FIGS. 5A and 5B are diagrams showing the laser beam shape and apositional relation between the laser beam and a sub-island;

[0037]FIGS. 6A to 6D are diagrams showing the positional relationbetween a portion irradiated with laser light and a mask;

[0038]FIGS. 7A and 7B are diagrams showing the positional relationbetween a portion irradiated with laser light and a mask;

[0039]FIGS. 8A and 8B are diagrams showing the positional relationbetween a laser light moving direction on a processing object and amask;

[0040]FIGS. 9A and 9B are diagrams showing the positional relationbetween a portion irradiated with laser light and a mask;

[0041]FIG. 10 is a diagram of a laser irradiation apparatus;

[0042]FIG. 11 is a diagram of a laser irradiation apparatus;

[0043]FIG. 12 is a diagram showing production flow of the presentinvention;

[0044]FIG. 13 is a diagram showing the production flow of the presentinvention;

[0045]FIG. 14 is a diagram showing the production flow of the presentinvention;

[0046]FIG. 15 is a diagram showing the production flow of prior art;

[0047]FIGS. 16A and 16B are diagrams showing the positional relationbetween a slit and a beam spot;

[0048]FIGS. 17A to 17D are diagrams each showing an optical system oflaser irradiation apparatus;

[0049]FIGS. 18A and 18B are diagrams showing the positional relationbetween a portion irradiated with laser light and a mask;

[0050]FIGS. 19A to 19D are diagrams showing directions of laser lightmoving on a processing object;

[0051]FIG. 20 is a diagram showing a direction of laser light moving ona processing object;

[0052]FIG. 21 is a diagram showing the energy density distribution in acentral axis direction of overlapping beam spots;

[0053]FIGS. 22A to 22C are diagrams showing how beam spots areoverlapped;

[0054]FIGS. 23A to 23D are diagrams showing a method of manufacturing asemiconductor device which uses a laser irradiation method of thepresent invention;

[0055]FIGS. 24A to 24C are diagrams showing a method of manufacturing asemiconductor device which uses a laser irradiation method of thepresent invention;

[0056]FIGS. 25A to 25C are diagrams showing a method of manufacturing asemiconductor device which uses a laser irradiation method of thepresent invention;

[0057]FIG. 26 is a diagram showing a method of manufacturing asemiconductor device which uses a laser irradiation method of thepresent invention;

[0058]FIG. 27 is a diagram of a liquid crystal display devicemanufactured by using a laser irradiation method of the presentinvention;

[0059]FIGS. 28A and 28B are diagrams showing a method of manufacturing alight emitting device which uses a laser irradiation method of thepresent invention;

[0060]FIG. 29 is a sectional view of a light emitting device using alaser irradiation method of the present invention;

[0061]FIG. 30 is a diagram showing the production flow of the presentinvention;

[0062]FIG. 31 is a diagram showing a method of manufacturing a lightemitting device which uses a laser irradiation method of the presentinvention;

[0063]FIG. 32 is a diagram showing the production flow of the presentinvention;

[0064]FIG. 33 is a sectional view of a light emitting device using alaser irradiation method of the present invention;

[0065]FIGS. 34A to 34L are diagrams showing a method of manufacturing asemiconductor device which uses a laser irradiation method of thepresent invention;

[0066]FIGS. 35A to 35G are diagrams showing a method of manufacturing asemiconductor device which uses a laser irradiation method of thepresent invention;

[0067]FIGS. 36A to 36G are diagrams showing a method of manufacturing asemiconductor device which uses a laser irradiation method of thepresent invention;

[0068]FIGS. 37A to 37C are diagrams showing a method of manufacturing asemiconductor device which uses a laser irradiation method of thepresent invention;

[0069]FIG. 38 is a graph showing the energy difference in relation tothe distance between centers of beam spots;

[0070]FIG. 39 is a graph showing the output energy distribution in thecentral axis direction of a beam spot;

[0071]FIGS. 40A and 40B are diagrams of a panel with a driving circuitmounted thereto; and

[0072]FIG. 41 is a sectional view of a light emitting devicemanufactured by using a laser apparatus of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0073] Embodiment Mode

[0074] Descriptions will be given below on a laser irradiation methodand semiconductor device manufacturing method of the present inventionwith reference to FIGS. 1A to 1D.

[0075] First, as shown in FIG. 1A, a semiconductor film 11 is formed ona substrate 10. The substrate 10 can be any material as long as it canwithstand the processing temperature in later steps. For example, aquartz substrate, silicon substrate, glass substrate, metal substrate,or stainless steel substrate with an insulating film formed on itssurface can be employed. The glass substrate is formed of bariumborosilicate glass, aluminoborosilicate glass, or the like. A plasticsubstrate may also be employed if it has enough heat resistance towithstand the processing temperature.

[0076] An insulating film is formed between the substrate 10 and thesemiconductor film 11 to serve as a base film for preventing an alkalinemetal or other impurities contained in the substrate 10 from enteringthe semiconductor film 11.

[0077] The semiconductor film 11 can be formed by a known method(sputtering, LPCVD, plasma CVD, or the like). The semiconductor film maybe an amorphous semiconductor film, a microcrystalline semiconductorfilm, or a crystalline semiconductor film.

[0078] Next, the semiconductor film 11 is patterned as shown in FIG. 1Bto form a sub-island (before laser crystallization (Pre-LC)) 12 and amarker 19. The shape of the marker is not limited to the one shown inFIG. 1B.

[0079] The sub-island (Pre-LC) 12 is then irradiated with laser light asshown in FIG. 1C to form a sub-island (Post-LC) 13 with enhancedcrystallinity. In the present invention, a portion of a beam spot thatis low in energy density is cut off by a slit 17. The slit 17 isdesirably formed of a material that can block laser light and is notdeformed or damaged by laser light. The width of the slit in the slit 17is variable and a beam spot can be changed in width by changing thewidth of the slit.

[0080] A laser beam is judged as being low in energy density when itdoes not meet the value necessary to obtain desired crystals. Whether acrystal qualifies as a desired crystal or not is appropriately decidedat designer's discretion. Therefore, if a laser beam cannot provide thecrystallinity that the designer wants, the laser beam is judged as beinglow in energy density.

[0081] The laser light energy density is lower in the vicinity of edgesof a beam spot that has passed through the slit. The vicinity of edgestherefore can only provide small crystal grains and causes a ridge alongthe grain boundary. For that reason, edges 15 of the track of a beamspot 14 of laser light has to be prevented from overlapping thesub-island (Pre-LC) 12 or an island formed after the sub-island.

[0082] The laser light scanning direction is determined such that, asthe beam spot reaches the sub-island during laser light scanning, onepoint of the beam spot comes into contact with the sub-island viewedfrom the direction perpendicular to the substrate. Laser lightirradiation is started from the one contact point to commence growth ofcrystals having <100> orientation from the vicinity of the contactpoint. When irradiation of the sub-island with laser light is finished,the <100> orientation ratio of the entire sub-island is now improved.

[0083] The present invention can employ known lasers. A pulseoscillation or continuous wave gas laser or solid-state laser may beemployed. Examples of the gas laser include an excimer laser, an Arlaser, and a Kr laser. Examples of the solid-state laser include a YAGlaser, a YVO₄ laser, a YLF laser, a YAlO₃ laser, a glass laser, a rubylaser, an alexandrite laser, a Ti: sapphire laser, and a Y₂O₃ laser. Thesolid-state laser employed is a laser that uses crystals of YAG, YVO₄,YLF, YAlO₃ or the like doped with Cr, Nd, Er, Ho, Ce, Co, Ti, Yb, or Tm.The fundamental wave of the laser is varied depending on the materialused for doping but laser light obtained has a fundamental wave of about1 μm. A non-linear optical element is used to obtain harmonic of thefundamental wave.

[0084] Ultraviolet laser light may also be employed. The ultravioletlaser light is obtained by using a non-linear optical element to convertinfrared laser light that is emitted from a solid-state laser into greenlaser light and then using another non-linear optical element to convertthe green laser light.

[0085] The marker 19 may not be irradiated with laser light.

[0086] Next, the sub-island (Post-LC) 13 is patterned as shown in FIG.1D to form an island 16. Desirably, a portion at the center of thesub-island that has better crystallinity is used to form the island 16while discarding the vicinity of edges of the sub-island. The marker 19is not removed by the patterning but is left for mask positioning in alater step.

[0087] The island 16 formed through the above steps has excellentcrystallinity as well as enhanced <100> orientation ratio.

[0088] The description given next is about the shape of a beam spotsynthesized by overlapping plural beam spots.

[0089]FIG. 4A shows an example of the beam spot shape on a processingobject when laser light emitted from plural laser oscillationapparatuses does not pass through a slit. The beam spot shown in FIG. 4Ahas an elliptical shape. In the present invention, the beam spot shapeof laser light emitted from laser oscillation apparatus is not limitedto an ellipse. The beam spot shape is varied depending on the laser typeand may be shaped by an optical system. For instance, the shape of laserlight emitted from the XeCl excimer laser (wavelength: 308 nm, pulsewidth: 30 ns) L3308, a product of Lambda Physik, is a 10 mm×30 mm (eachis half width in beam profile) rectangle. The shape of laser lightemitted from a YAG laser is circular if the rod is cylindrical and isrectangular if the rod is slab-like. Such laser light may be furthershaped by an optical system to give the laser light a desired size.

[0090]FIG. 4B shows the energy density distribution of laser light inthe direction of a major axis Y of the beam spot shown in FIG. 4A. Theenergy density distribution of laser light whose beam spot has anelliptical shape becomes higher toward a center O of the ellipse. αcorresponds to the width in the direction of a major axis Y where theenergy density exceeds the value necessary to obtain desired crystals.

[0091]FIG. 2A shows the beam spot shape of when laser light that havethe beam spot shown in FIGS. 4A and 4B are synthesized. In the caseshown in FIG. 2A, one linear beam spot is formed by overlapping fourlaser beam spots. However, the number of beam spots overlapped is notlimited thereto.

[0092] As shown in FIG. 2A, the beam spots of the laser beams aresynthesized by lining the ellipses up along their major axes to havethem partially overlapped with one another. One beam spot 18 is thusformed. Hereinafter, the straight line obtained by connecting centers Oof the ellipses will be called a central axis.

[0093]FIG. 2B shows the laser light energy density distribution in acentral axis y of the synthesized beam spot shown in FIG. 2A. The beamspot shown in FIG. 2A corresponds to a region that meets the peak energydensity 1/e² in FIG. 2B. In the portions where the beam spots beforesynthesization overlap one another, the energy density is added. Forinstance, as shown in the drawing, energy densities E1 and E2 of theoverlapping beams are added and the sum is almost equal to the peakenergy density of the beam, E3. The energy density is thus evened outbetween the centers O of the ellipses.

[0094] The sum of E1 and E2 is ideally E3 but this is not always true inpractice. The acceptable deviation of the sum of E1 and E2 from E3 canbe set appropriately at designer's discretion.

[0095] As FIG. 2B shows, the crystallinity of a semiconductor film canbe enhanced more efficiently when plural laser beams are overlapped tocompensate one another's low energy density portions than when using asingle laser beam. Assume that the energy density value necessary toobtain desired crystals is met only in the hatched regions of FIG. 1Band not in the rest as a result of irradiation by a single beam spot. Inthis case, only a hatched region of the beam spot whose width in thecentral axis direction is α can provide desired crystals. If beam spotsare overlapped instead as shown in FIG. 2B, a region whose width in thecentral axis direction is β (β>4α) can provide desired crystals and asemiconductor film can be crystallized more efficiently.

[0096] The energy density distributions in B-B′ and C-C′ of FIG. 2A arecalculated and shown in FIGS. 3A and 3B, respectively. In FIGS. 3A and3B, regions of beam spots before synthesization where the peak energydensity 1/e² is met are used as the reference. The energy densitydistributions in B-B′ and C-C′ shown in FIGS. 3A and 3B are of when eachbeam spot before synthesization measures 37 μm in length in the minoraxis direction and 410 μm in length in the major axis direction and thedistance between centers of the beam spots is set to 192 μm. Althoughthe distribution in B-B′ is slightly smaller than the distribution inC-C′, the two have almost the same size. Therefore, it can be said thatthe shape of the synthesized beam spot is linear in the regions of thebeam spots before synthesization where the peak energy density 1/e² ismet.

[0097] There are regions where the energy density fails to meet thedesired value even after laser beams are overlapped. The presentinvention uses the slit 17 to cut off the low energy density regions ofthe synthesized beam spot and prevents them from irradiating thesemiconductor film 11. The positional relation between the synthesizedbeam spot and the slit is described with reference to FIG. 2C.

[0098] The slit 17 used in the present invention has a slit variable inwidth and the width is controlled by a computer. In FIG. 2C, 18 denotesthe shape of the beam spot 18 obtained by synthesization as the oneshown in FIG. 2A and 17 denotes the slit.

[0099]FIG. 2D shows the energy density distribution in a direction ythat is the direction of the central axis A-A′ of the beam spot shown inFIG. 2B. Unlike the case shown in FIG. 3B, regions low in energy densityare cut off by the slit 17.

[0100] A semiconductor film irradiated with a region of laser light thatis low in energy density has poor crystallinity. Specifically, crystalgrains of such film are smaller in size than ones in a film irradiatedwith a laser light region having enough energy density and the crystalgrains grow in different directions. FIG. 5A shows the shape of asynthesized beam spot on a substrate. In a region denoted by 50, adesired energy density is met. A region denoted by 51 does not meet thedesired energy density. The length in the central axis direction of thebeam spot is given as W_(TBW), the length in the central axis directionof the region having enough energy density is given as W_(BW), and thelength in the direction perpendicular to the central axis direction ofthe region having enough energy density is given as W_(C).

[0101]FIG. 5B shows the positional relation between the scanning path ofa beam spot 52 and a sub-island pattern. The length in the central axisdirection of the beam spot 52 is set equal to or less than W_(BW) bymaking the beam spot shown in FIG. 5A travel through a slit. FIG. 5Bshows scanning by the beam spot 52 whose low energy density portions arecut off widthwise in the direction perpendicular to the scanningdirection. The beam spot 52 runs so as to cover a sub-island 53 andedges of the track of the beam spot does not overlap the sub-island 53.It is not always necessary to prevent the edges of the track of the beamspot from overlapping the sub-island. What is important is to preventthe edges from overlapping an island 54 that is obtained through theminimum patterning of the sub-island.

[0102] In the present invention, there is no low energy density region,or if there is any, the width thereof is smaller than in the case wherea slit is not used. This makes it easier to avoid overlapping of laserlight edges and the sub-island 53. By using a slit, regions low inenergy density are cut off and therefore limitations in setting thelaser light scanning path and layout of a sub-island and island can bereduced.

[0103] Also the present invention can prevent laser light edges fromoverlapping an island or its channel formation region because the beamspot width can be changed without stopping output of laser oscillationapparatus while keeping the energy density constant. A portion that doesnot need laser irradiation is not irradiated with laser light andtherefore damage to the substrate can be avoided.

[0104] In the case shown in FIGS. 5A and 5B, the central axis directionof the beam spot is kept perpendicular to the scanning direction.However, it is not always necessary to set the central axis direction ofthe beam spot perpendicular to the scanning direction. For example, anacute angle θ_(A) formed between the central axis direction of the beamspot and the scanning direction may be set to 45°±35°, desirably 45°.The substrate processing efficiency is the highest when the central axisof a beam spot is perpendicular to the scanning direction. On the otherhand, when the central axis of a synthesized beam spot and the scanningdirection form an angle of 45°±35°, desirably closer to 45°, crystalgrains present in the active layer can be increased in number than whenthe central axis of the beam spot is perpendicular to the scanningdirection. Accordingly, fluctuation in characteristic due to crystalorientation and crystal grains can be reduced. In addition, if thescanning speed is the same, the laser light irradiation time persubstrate is longer when the central axis of a synthesized beam spot andthe scanning direction form an angle of 45°±35° than when the centralaxis of the beam spot is perpendicular to the scanning direction.

[0105] Next, a description is given on the relation between the shapesof a sub-island and island and the laser light scanning direction. FIG.6A is a top view of the sub-island 12 shown in FIG. 1B. A portion 16 tobe an island is indicated by a dashed line inside the sub-island(Pre-LC) 12. Denoted by 14 is a beam spot, which in FIG. 6A is in astate before laser irradiation.

[0106] From the state in FIG. 6A, the beam spot 14 approaches thesub-island (Pre-LC) 12 as time passes. The position of the beam spot ischanged by moving the substrate.

[0107] As the beam spot 14 reaches the sub-island (Pre-LC) 12, one pointof the beam spot 14 comes into contact with the sub-island (Pre-LC) 12.Crystallization of the sub-island begins from the vicinity of thiscontact point, which is denoted by 20, and the crystallization proceedsin the direction indicated by the arrow as the beam spot 14 moves asshown in FIG. 6C. Since the crystallization starts from a seed crystalformed in the contact point vicinity 20 first, the <110> orientationratio is raised.

[0108] When the island is used as an active layer of a TFT, the laserlight scanning direction is desirably kept parallel to the direction inwhich carriers of a channel formation region move.

[0109] The track of the beam spot 14 may not completely cover thesub-island 12, and it only has to cover the island 16 completely.However, by running laser light so as to completely cover thesub-island, a region that is not irradiated with laser light isprevented from working as a seed crystal for crystal growth and the<110> orientation ratio can be enhanced more.

[0110]FIG. 6D shows a sectional view taken along the line A-A′ of FIG.6C in relation to the beam spot. Laser light that has passed through theslit 17 to irradiate the substrate is partially blocked by the slit andits width W_(TDW) in the major axis direction is reduced to W_(BW).Then, ideally, the beam spot of the laser light on the sub-islandbecomes equal in width with W_(BW). However, the slit 17 is actuallydistanced from the sub-island 12 and therefore the actual width in themajor axis direction of the beam spot of the laser light is W_(BW)′ onthe sub-island 12. W_(BW)′ is smaller than W_(BW). (W_(BW)′<W_(BW)).Therefore, it is desirable to set the slit width taking diffraction intoconsideration.

[0111] In irradiating the entire sub-island with laser light, it issufficient if W_(BW)>W_(S) is satisfied when diffraction is not takeninto account and W_(BW)′>W_(S) is satisfied when diffraction is takeninto account. In the minimum laser irradiation for irradiating theisland alone, it is sufficient if W_(BW)>W_(I) is satisfied whendiffraction is not taken into account and W_(BW)′>W_(I) is satisfiedwhen diffraction is taken into account. W_(S) is the longest length ofthe sub-island 12 in the direction perpendicular to the moving directionof the beam spot. W_(I) represents the longest length of the island 16in the direction perpendicular to the moving direction of the beam spot.

[0112]FIGS. 7A and 7B show examples of layout of an island used as anactive layer of a TFT in relation to the moving direction of a beamspot. In FIG. 7A, a portion 31 indicated by the dashed line inside asub-island 30 becomes an island. When the island 31 is used as an activelayer of a TFT which has one channel formation region, impurity regions33 and 34 are provided so as to sandwich a channel formation region 32.One of the impurity regions 33 and 34 serves as a source region and theother serves as a drain region. The reference numeral 35 shows the shapeof the beam spot. In crystallizing the sub-island 30, the laser lightscanning direction is set parallel to the direction in which carriers ofthe channel formation region 32 move as indicated by the arrow. Onepoint of the beam spot 35 is in contact with the sub-island. A seedcrystal is formed in the vicinity of the contact point, which is denotedby 36, and crystals grow from the seed crystal. The <110> orientationratio of the sub-island is thus enhanced.

[0113]FIG. 7B shows an active layer having three channel formationregions. Impurity regions 41 and 42 are provided so as to sandwich achannel formation region 40. The impurity region 42 and an impurityregion 44 are provided so as to sandwich a channel formation region 43.The impurity region 44 and an impurity region 46 are provided so as tosandwich a channel formation region 45. The beam spot runs in parallelto the direction in which carriers of the channel formation regions 40,43, and 45 move as indicated by the arrow.

[0114] Described next with reference to FIG. 8A is the laser lightscanning direction on a substrate 500 where a sub-island is formed tomanufacture an active matrix semiconductor device. In FIG. 8A, a pixelportion, a signal line driving circuit, and a scanning line drivingcircuit are formed in the areas indicated by dashed lines 501, 502, and503, respectively.

[0115] In the example shown in FIG. 8A, laser light runs over thesubstrate 500 only once. The substrate moves in the direction indicatedby the outlined arrow and the solid line arrow indicates the relativelaser light scanning direction. The beam spot may be moved by moving thesubstrate 500 or by using an optical system. FIG. 8B is an enlarged viewof a beam spot 507 in the area 501 where the pixel portion is to beformed. Sub-islands 506 are laid out in a region irradiated with laserlight.

[0116] It is desirable in FIGS. 8A and 8B to irradiate the substratewith laser light so as to prevent edges of the beam spot fromoverlapping islands 508, more desirably, the sub-islands 506. Theislands 508 are obtained by patterning the sub-islands. In the presentinvention, which portion is to be scanned with laser light is determinedin accordance with pattern information of a mask of a sub-island.

[0117] The beam spot width can be changed to suite the size of asub-island or island. For example, in a TFT of a driving circuit where arelatively large amount of current flows, the channel width is large andaccordingly the island size tends to be larger than in a pixel portion.In FIGS. 9A and 9B, the slit width is changed to run laser light overtwo types of sub-islands having different sizes. FIG. 9A shows therelation between a portion scanned with laser light and a sub-islandwhen the sub-island is shorter in the direction perpendicular to thescanning direction. FIG. 9B shows the relation between a portion scannedwith laser light and a sub-island when the sub-island is longer in thedirection perpendicular to the scanning direction.

[0118] When the beam spot width in FIG. 9A is given as W_(BW1) and thebeam spot width in FIG. 9B is given as W_(BW2), W_(BW1) is smaller thanW_(BW2). The beam spot width is not limited thereto and can be setfreely if there is a margin in the gap between sub-islands in thedirection perpendicular to the scanning direction.

[0119] The present invention runs laser light so as to obtain theminimum degree of crystallization of a sub-island as shown in FIGS. 9Aand 9B, instead of irradiating the entire surface of the substrate withlaser light. Since the minimum portion is irradiated with laser light sothat a sub-island is crystallized instead of irradiating the entiresurface of a substrate, the processing time per substrate can be reducedto raise the substrate processing efficiency.

[0120] Next, a description is given with reference to FIG. 10 on thestructure of laser irradiation apparatus used in the present invention.The reference numeral 101 denotes a laser oscillation apparatus. Fourlaser oscillation apparatuses are used in FIG. 10 but the number oflaser oscillation apparatuses in the laser irradiation apparatus is notlimited thereto.

[0121] A chiller 102 may be used to keep the temperature of the laseroscillation apparatus 101 constant. Although the chiller 102 is notalways necessary, fluctuation in energy of laser light outputted due toa temperature change can be avoided by keeping the temperature of thelaser oscillation apparatus 101 constant.

[0122] Denoted by 104 is an optical system, which changes the path oflight emitted from the laser oscillation apparatus 101 or manipulatesthe shape of its beam spot to collect laser light. In the laserirradiation apparatus of FIG. 10, the optical system 104 can alsosynthesize beam spots of laser light outputted from the plural laseroscillation apparatuses 101 by partially overlapping the beam spots.

[0123] An AO modulator 103 capable of changing the travel direction oflaser light in a very short time may be provided in the light pathbetween a substrate 106 that is a processing object and the laseroscillation apparatus 101. Instead of the AO modulator, an attenuator(light amount adjusting filter) may be provided to adjust the energydensity of laser light.

[0124] Alternatively, energy density measuring means 115, namely, meansfor measuring the energy density of laser light outputted from the laseroscillation apparatus 101 may be provided in the light path between thesubstrate 106 that is a processing object and the laser oscillationapparatus 101. Changes with time of measured energy density aremonitored by a computer 110. In this case, output from the laseroscillation apparatus 101 may be increased to compensate attenuation inenergy density of the laser light.

[0125] A synthesized beam spot irradiates through a slit 105 thesubstrate 106 that is a processing object. The slit 105 is desirablyformed of a material that can block laser light and is not deformed ordamaged by laser light. The width of the slit in the slit 105 isvariable and a beam spot can be changed in width by changing the widthof the slit.

[0126] When laser light emitted from the laser oscillation apparatusdoes not pass through the slit 105, the shape of its beam spot on thesubstrate 106 is varied depending on the laser type and may be shaped byan optical system.

[0127] The substrate 106 is set on a stage 107. In FIG. 10, positioncontrolling means 108 and 109 correspond to means for controlling theposition of a beam spot on a processing object. The position of thestage 107 is controlled by the position controlling means 108 and 109.

[0128] In FIG. 10, the position controlling means 108 controls theposition of the stage 107 in the direction X and the positioncontrolling means 109 controls the position of the stage 107 in thedirection Y.

[0129] The laser irradiation apparatus of FIG. 10 has the computer 110,which is a central processing unit and at the same time storing meanssuch as a memory. The computer 110 controls oscillation of the laseroscillation apparatus 101 and controls the position controlling means108 and 109 to move the substrate to a given position so that a beamspot of laser light covers a region determined in accordance with maskpattern information.

[0130] In the present invention, the computer 110 also controls thewidth of the slit 105 so that the beam spot width can be changed inaccordance with mask pattern information.

[0131] The laser irradiation apparatus may also has means for adjustingthe temperature of a processing object. A damper may also be provided toprevent reflected light from irradiating a portion that should avoidlaser irradiation since laser light is highly directional and has highenergy density. Desirably, the damper is absorptive of reflected light.Cooling water may be circulated inside the damper to avoid a temperaturerise of the partition wall due to absorption of reflected light. Thestage 107 may be provided with means for heating a substrate (substrateheating means).

[0132] If a laser is used to form a marker, laser oscillation apparatusfor a marker may be provided. In this case, oscillation of the laseroscillation apparatus for a marker may be controlled by the computer110. Another optical system is needed when the laser oscillationapparatus for a marker is provided in order to collect laser lightoutputted from the laser oscillation apparatus for a marker. The laserused to form a marker is typically a YAG laser or a CO₂ laser but otherlasers may be employed.

[0133] One or more CCD cameras 113 may be provided for positioning usinga marker.

[0134] Instead of forming a marker, the CCD camera(s) 113 may be used torecognize the pattern of a sub-island for positioning. In this case,sub-island pattern information by a mask which is inputted to thecomputer 110 and the actual sub-island pattern information collected bythe CCD camera(s) 113 are checked against each other to obtain thesubstrate position information.

[0135] Although FIG. 10 shows a structure of a laser irradiationapparatus which has plural laser oscillation apparatuses, only one laseroscillation apparatus may be provided. FIG. 11 shows a laser irradiationapparatus structure which has one laser oscillation apparatus. In FIG.11, 201 denotes a laser oscillation apparatus and 202 denotes a chiller.Denoted by 215 is an energy density measuring device, 203, an AOmodulator, 204, an optical system, 205, a slit, and 213, a CCD camera. Asubstrate 206 is set on a stage 207. The position of the stage 207 iscontrolled by X-direction position controlling means 208 and Y-directionposition controlling means 209. Similar to the apparatus shown in FIG.10, a computer 210 controls operations of the respective means of thislaser irradiation apparatus. The major difference between FIG. 11 andFIG. 10 is that there is one laser oscillation apparatus in FIG. 11.Unlike FIG. 10, the optical system 204 only has to have a function ofcollecting one laser beam.

[0136] Next, the flow of a semiconductor device manufacturing method ofthe present invention will be described.

[0137]FIG. 12 is a flow chart showing production flow. First, asemiconductor device is designed using CAD. Specifically, a mask for anisland is designed first and then a mask for a sub-island that includesone or more of such islands is designed. In designing the masks, allislands included in one sub-island are desirably arranged such that thecarriers of their channel formation regions move in the same direction.However, the moving direction may be varied intentionally if doing sosuits the use of the semiconductor device.

[0138] The mask for a sub-island may be designed such that a marker isformed at the same time the sub-island is formed.

[0139] Then, information concerning the shape of the designed mask for asub-island (pattern information) is inputted to a computer of laserirradiation apparatus. From the sub-island pattern information inputted,the computer calculates a width W_(S) of each sub-island in thedirection perpendicular to the scanning direction. Based on the widthW_(S) of each sub-island, a slit width W_(BW) in the directionperpendicular to the scanning direction is set.

[0140] Then, the laser light scanning path is determined based on theslit width W_(BW) with the marker position as the reference.

[0141] During this, a semiconductor film is formed on a substrate andthe semiconductor film is patterned using the mask for a sub-island toform a sub-island. The substrate on which the sub-island is formed isset on a stage of the laser irradiation apparatus.

[0142] With the marker as the reference, laser light runs along the setscanning path targeting the sub-island to crystallize the sub-island.

[0143] The sub-island having its crystallinity enhanced by the laserlight irradiation is patterned to form an island. Subsequently, aprocess of manufacturing a TFT from the island follows. Althoughspecifics of the TFT manufacturing process are varied depending on theTFT form, a typical process starts with forming a gate insulating filmand forming an impurity region in the island. Then, an interlayerinsulating film is formed so as to cover the gate insulating film and agate electrode. A contact hole is formed in the interlayer insulatingfilm to partially expose the impurity region. A wiring is then formed onthe interlayer insulating film to reach the impurity region through thecontact hole.

[0144] Described next is an example of positioning a substrate and amask by a CCD camera without forming a marker.

[0145]FIG. 13 is a flow chart showing production flow. First, similar tothe case of FIG. 12, a semiconductor device is designed using CAD.Specifically, a mask for an island is designed first and then a mask fora sub-island that includes one or more of such islands is designed.

[0146] Then, information concerning the shape of the designed mask for asub-island (pattern information) is inputted to a computer of laserirradiation apparatus. From the sub-island pattern information inputted,the computer calculates a width W_(S) of each sub-island in thedirection perpendicular to the scanning direction. Based on the widthW_(S) of each sub-island, a slit width W_(BW) in the directionperpendicular to the scanning direction is set.

[0147] During this, a semiconductor film is formed on a substrate andthe semiconductor film is patterned using the mask for a sub-island toform a sub-island. The substrate on which the sub-island is formed isset on a stage of the laser irradiation apparatus.

[0148] Then, pattern information of the sub-island formed on thesubstrate that is set on the stage is detected by the CCD camera andinputted to the computer. The computer checks the pattern information ofthe sub-island actually formed on the substrate which is obtained by theCCD camera against the pattern information of the sub-island designed bythe CAD for positioning of the substrate and the mask.

[0149] The laser light scanning path is determined based on the slitwidth W_(BW) and the sub-island position information provided by the CCDcamera.

[0150] Then, laser light runs along the set scanning path targeting thesub-island to crystallize the sub-island.

[0151] The sub-island having its crystallinity enhanced by the laserlight irradiation is patterned to form an island. Subsequently, aprocess of manufacturing a TFT from the island follows. Althoughspecifics of the TFT manufacturing process are varied depending on theTFT form, a typical process starts with forming a gate insulating filmand forming an impurity region in the island. Then, an interlayerinsulating film is formed so as to cover the gate insulating film and agate electrode. A contact hole is formed in the interlayer insulatingfilm to partially expose the impurity region. A wiring is then formed onthe interlayer insulating film to reach the impurity region through thecontact hole.

[0152]FIG. 14 is a flow chart showing the flow of a producing method inwhich a processing object is irradiated with laser light twice.

[0153] First, a semiconductor device is designed using CAD.Specifically, a mask for an island is designed first and then a mask fora sub-island that includes one or more of such islands is designed. Themask for a sub-island may be designed such that a marker is formed atthe same time the sub-island is formed.

[0154] Then, information concerning the shape of the designed mask for asub-island (pattern information) is inputted to a computer of laserirradiation apparatus. From the sub-island pattern information inputted,the computer calculates for each sub-island two widths W_(S) in thedirections perpendicular to two scanning directions. Slit widths W_(BW)in the directions perpendicular to the two scanning directions arecalculated based on the widths W_(S) of each sub-island.

[0155] Then, the laser light scanning path in each of the two scanningdirections is determined based on the respective slit widths W_(BW) withthe marker position as the reference.

[0156] During this, a semiconductor film is formed on a substrate andthe semiconductor film is patterned using the mask for a sub-island toform a sub-island. The substrate on which the sub-island is formed isset on a stage of the laser irradiation apparatus.

[0157] With the marker as the reference, a first laser light runs alonga first scanning path, namely, one of the two scanning paths set,targeting the sub-island to crystallize the sub-island.

[0158] The angle the first time laser light scanning direction and thesecond time laser light scanning direction form may be stored in advancein a memory or the like, or may be inputted manually as the need arises.

[0159] The scanning direction is then changed and the second laser lightruns along the second scanning path targeting the sub-island tocrystallize the sub-island.

[0160] In the example shown in FIG. 14, the same sub-island is twiceirradiated with laser light. However, it is also possible to change thescanning direction specifying the location if an AO modulator or thelike is employed. For instance, when the scanning direction in a signalline driving circuit is different from the scanning direction in a pixelportion and a scanning line driving circuit and an AO modulator is usedto irradiate with laser light an area to become the signal line drivingcircuit, the AO modulator prevents laser light from irradiating areas tobecome the pixel portion and the scanning line driving circuit. Ifinstead the areas to become the pixel portion and the scanning linedriving circuit are irradiated with laser light, the AO modulatorprevents laser light from irradiating the area to become the signal linedriving circuit. In this case, the computer synchronizes the AOmodulator with the position controlling means.

[0161] The sub-island having its crystallinity enhanced by the laserlight irradiation is patterned to form an island. Subsequently, aprocess of manufacturing a TFT from the island follows. Althoughspecifics of the TFT manufacturing process are varied depending on theTFT form, a typical process starts with forming a gate insulating filmand forming an impurity region in the island. Then, an interlayerinsulating film is formed so as to cover the gate insulating film and agate electrode. A contact hole is formed in the interlayer insulatingfilm to partially expose the impurity region. A wiring is then formed onthe interlayer insulating film to reach the impurity region through thecontact hole.

[0162] For comparison, the flow of a conventional semiconductor deviceproducing method is shown in FIG. 15. As shown in FIG. 15, a mask of asemiconductor device is designed using CAD. An amorphous semiconductorfilm is formed on a substrate, and the substrate on which the amorphoussemiconductor film is formed is set in laser irradiation apparatus.Then, laser light runs over the substrate so that the entire amorphoussemiconductor film is irradiated with laser light. As a result, theentire amorphous semiconductor film is crystallized. A marker is formedin the polycrystalline semiconductor film obtained by thecrystallization, and the polycrystalline semiconductor film is patternedwith the marker as the reference to form an island. Then, a TFT isformed from the island.

[0163] As described, unlike prior art as the one shown in FIG. 15, thepresent invention uses laser light to form a marker before an amorphoussemiconductor film is crystallized. The present invention then runslaser light in accordance with information of a mask for patterning ofthe semiconductor film.

[0164] With the above structure, time for laser irradiation of portionsthat are removed by patterning after crystallization of thesemiconductor film can be saved to shorten the whole laser irradiationtime and improve the substrate processing speed.

[0165] A step of crystallizing a semiconductor film using a catalyst maybe included. If a catalytic element is used, it is desirable to employtechniques disclosed in JP 07-130652 A and JP 08-78329 A.

[0166] When a step of crystallizing a semiconductor film using acatalyst is included, the process includes a step of crystallizing anamorphous semiconductor film by using Ni after the film is formed(NiSPC). For example, if the technique disclosed in JP 07-130652 A isused, a nickel acetate solution containing 10 ppm of nickel by weight isapplied to an amorphous semiconductor film to form a nickel-containinglayer. After a dehydrogenation step at 500° C. for an hour, theamorphous semiconductor film is subjected to heat treatment at 500 to650° C. for 4 to 12 hours, for example, at 550° C. for 8 hours, forcrystallization. Examples of other employable catalytic elements thannickel (Ni) include germanium (Ge), iron (Fe), palladium (Pd), tin (Sn),lead (Pb), cobalt (Co), platinum (Pt), copper (Cu), and gold (Au).

[0167] The crystallinity of the semiconductor film that has beencrystallized through NiSPC is further enhanced by laser lightirradiation. The polycrystalline semiconductor film obtained by thelaser light irradiation contains the catalytic element, which is removedfrom the crystalline semiconductor film by gettering after the laserlight irradiation. For gettering, a technique disclosed in JP 10-135468A or JP 10-135469 A can be employed.

[0168] To be specific, a part of the polycrystalline semiconductor filmobtained through the laser irradiation is doped with phosphorus and thensubjected to heat treatment at 550 to 800° C. for 5 to 24 hours, forexample, at 600° C. for 12 hours in a nitrogen atmosphere. This causesthe phosphorus-doped region of the polycrystalline semiconductor film toact as a gettering site, so that nickel present in the polycrystallinesemiconductor film is moved to the phosphorus-doped region andsegregated. After that, the phosphorus-doped region of thepolycrystalline semiconductor film is removed by patterning to obtain anisland in which the catalytic element concentration is reduced down to1×10¹⁷ atoms/cm³ or less, preferably, 1×10¹⁶ atoms/cm³ or less.

[0169] Next, a description is given with reference to FIGS. 16A and 16Bon the positional relation between a slit and a beam spot when thecentral axis of the beam spot is kept at 45° with respect to thescanning direction. Denoted by 130 is a beam spot after synthesizationand 105 denotes a slit. The slit 105 does not overlap the beam spot 130.The arrow indicates the scanning direction, which forms an angle θ withthe central axis of the beam spot 130. The angle θ is kept to 45°.

[0170]FIG. 16B shows a beam spot 131 obtained by partially blockinglaser light with the slit 105 to reduce the width. In the presentinvention, the slit 105 controls a width Q of a beam spot in thedirection perpendicular to the scanning direction for uniform laserlight irradiation.

[0171] As described, the present invention runs laser light so as toobtain at least the minimum degree of crystallization of a portion thathas to be crystallized, instead of irradiating the entire semiconductorfilm with laser light. With the above structure, time for laserirradiation of portions that are removed by patterning aftercrystallization of the semiconductor film can be saved to greatlyshorten the laser irradiation time per substrate.

[0172] Embodiments of the present invention will be described below.

[0173] Embodiment 1

[0174] This embodiment describes optical systems of laser irradiationapparatus used in the present invention, and the positional relationbetween a slit and each of the optical systems.

[0175]FIGS. 17A to 17D show optical systems of this embodiment. Theoptical system shown in FIG. 17A has two cylindrical lenses 401 and 402.Laser light entering from the direction indicated by the arrow passesthrough the two cylindrical lenses 401 and 402, which modify the shapeof the beam spot of the laser light. The beam spot travels through aslit 404 to irradiate a processing object 403. Of the cylindrical lenses401 and 402, 402 is closer to the processing object 403 and has ashorter focal length. In order to avoid return light and irradiateuniformly, the incident angle at which laser light enters the substrateis set to larger than 0°, desirably, 5 to 30°.

[0176] The optical system shown in FIG. 17B has a mirror 405 and aplanoconvex spherical lens 406. Laser light entering from the directionindicated by the arrow is reflected by the mirror 405, and the shape ofthe beam spot of the laser light is modified by the planoconvexspherical lens 406. The beam spot travels through a slit 408 toirradiate a processing object 407. The radius of curvature of theplanoconvex spherical lens can be set appropriately at designer'sdiscretion. In order to avoid return light and irradiate uniformly, theincident angle at which laser light enters the substrate is set tolarger than 0°, desirably, 5 to 30°.

[0177] The optical system shown in FIG. 17C has mirrors 410 and 411 andlenses 412, 413, and 414. Laser light entering from the directionindicated by the arrow is reflected by the mirrors 410 and 411, and theshape of the beam spot of the laser light is modified by the lenses 412,413, and 414. The beam spot travels through a slit 416 to irradiate aprocessing object 415. In order to avoid return light and irradiateuniformly, the incident angle at which laser light enters the substrateis set to larger than 0°, desirably, 5 to 30°.

[0178]FIG. 17D shows an optical system for synthesizing four beam spotsshown in Embodiment 2 to obtain one beam spot. The optical system shownin FIG. 17D has six cylindrical lenses 417 to 422. Four laser beamsentering the optical system from the directions indicated by the arrowsenter the four cylindrical lenses 419 to 422, respectively. Two laserbeams shaped by the cylindrical lenses 419 and 421 reach the cylindricallens 417, which modifies the shapes of their beam spots. The beam spotstravel through a slit 424 to irradiate a processing object 423. On theother hand, two laser beams shaped by the cylindrical lenses 420 and 422reach the cylindrical lens 418, which modifies the shapes of their beamspots. The beam spots travel through the slit 424 to irradiate theprocessing object 423.

[0179] The beam spots of the laser beams on the processing object 423partially overlap one another for synthesization, thereby forming onebeam spot.

[0180] The focal length and incident angle of each lens can be setappropriately at designer's discretion. However, the focal length of thecylindrical lenses 417 and 418 which are the closest to the processingobject 423 is set shorter than the focal length of the cylindricallenses 419 to 422. For example, the focal length of the cylindricallenses 417 and 418 which are the closest to the processing object 423 isset to 20 mm whereas the focal length of the cylindrical lenses 419 to422 is set to 150 mm. In this embodiment, the lenses are arranged suchthat laser beams enter the processing object 423 from the cylindricallenses 417 and 418 at an incident angle of 25° and laser beams enter thecylindrical lenses 417 and 418 from the cylindrical lenses 419 to 422 atan incident angle of 10°. In order to avoid return light and irradiateuniformly, the incident angle at which laser light enters the substrateis set to larger than 0°, desirably, 5 to 30°.

[0181] In the example shown in FIG. 17D, four beam spots aresynthesized. In this case, four cylindrical lenses respectivelyassociated with four laser oscillation apparatuses and two cylindricallenses associated with the four cylindrical lenses are provided. Thenumber of beam spots synthesized is not limited to 4. It is sufficientif the number of beam spots synthesized is equal to or more than 2 andequal to or less than 8. When n (n=2, 4, 6, 8) beam spots aresynthesized, n cylindrical lenses respectively associated with n laseroscillation apparatuses and n/2 cylindrical lenses associated with the ncylindrical lenses are provided. When n (n=3, 5, 7) beam spots aresynthesized, n cylindrical lenses respectively associated with n laseroscillation apparatuses and (n+1)/2 cylindrical lenses associated withthe n cylindrical lenses are provided.

[0182] When five or more beam spots are synthesized, the fifth and thefollowing laser beams desirably irradiate a substrate from the oppositeside of the substrate, taking into consideration where to place theoptical system, interference, and the like. In this case, another slitis needed on the opposite side of the substrate. Also, the substrate hasto be transmissive.

[0183] In order to prevent light from traveling back its light path(return light), the incident angle at which laser light enters thesubstrate is desirably kept at larger than 0° and smaller than 90°.

[0184] A plane which is perpendicular to the irradiated face and whichincludes a shorter side of the rectangular shape of each beam beforesynthesization, or a longer side thereof, is defined as an incidentplane. When the length of the shorter side or longer side included inthe incident plane is given as W, and the thickness of a substrate whichis transmissive of the laser light and which is set on the irradiatedface is given as d, an incident angle θ of the laser light desirablysatisfies θ≧arctan (W/2 d) to achieve uniform laser light irradiation.This has to be true in each laser light before synthesization. If thetrack of this laser light is not on the incident plane, the incidentangle of the track projected onto the incident plane is deemed as θ.When laser light enters the substrate at this incident angle θ,interference between light reflected at the front side of the substrateand reflected light from the back side of the substrate can be avoidedto give the substrate uniform laser beam irradiation. The premise of theabove discussion is that the refractive index of the substrate is 1. Inpractice, the refractive index of the substrate is often around 1.5, andthe angle calculated taken this fact into account is larger than theangle calculated in the above discussion. However, the energy of a beamspot is attenuated at its ends in the longitudinal direction andinfluence of interference is small in these portions. Therefore enoughinterference attenuation effect can be obtained with the valuecalculated in the above discussion.

[0185] An optical system of the laser irradiation apparatus used in thepresent invention can have other structures than those shown in thisembodiment.

[0186] Embodiment 2

[0187] This embodiment describes an example in which plural laseroscillation apparatuses are used and the width of a beam spot of laserlight is changed by an AO modulator in the middle of laser lightirradiation.

[0188] In this embodiment, a computer grasps a laser light scanning pathbased on mask information inputted. Furthermore, this embodiment uses anAO modulator to change the direction of laser light outputted from anyone of the plural laser oscillation apparatuses to prevent theredirected laser light from irradiating a processing object and therebychange the width of the beam spot in accordance with the mask shape. Inthis case, although the width of the beam spot is changed by the AOmodulator, a region of the beam spot that is low in energy density stillhas to be blocked in the direction perpendicular to the scanningdirection. Therefore, control of the slit width and blocking of laserlight by the AO modulator have to be synchronized.

[0189]FIG. 18A shows an example of the relation between the shape of amask for patterning a semiconductor film and the beam spot width when aprocessing object is irradiated with laser light once. Indicated by 560is the shape of a mask for patterning a semiconductor film. Asemiconductor film is patterned in accordance with the mask after thesemiconductor film is crystallized by laser irradiation.

[0190] Denoted by 561 and 562 are areas irradiated with laser light. Theareas 561 and 562 are scanned with a beam spot obtained by overlappingand synthesizing laser beams outputted from four laser oscillationapparatuses. A slit controls the beam spot width such that it isnarrower in 562 than in 561.

[0191] By using an AO modulator as in this embodiment, the beam spotwidth can be changed freely without stopping output of every laseroscillation apparatus and unstable output due to interruption of outputof laser oscillation apparatus can be avoided.

[0192] With the above structure, the laser light track can be changed inwidth and edges of the laser light track can be prevented fromoverlapping a semiconductor that is obtained by patterning. Also, theabove structure further reduces damage to a substrate which is caused byirradiating with laser light an area that does not need irradiation.

[0193] Next, a description is given on an example of blocking laserlight by an AO modulator in the middle of laser light irradiation toirradiate only a given area with laser light. In this embodiment, laserlight is blocked by using an AO modulator to change the direction of thelaser light. However, the present invention is not limited thereto andcan employ any measure that can block laser light.

[0194] In the present invention, a computer grasps which part is to bescanned with laser light from mask information inputted. Furthermore,this embodiment uses an AO modulator to change the direction of laserlight so that the laser light is blocked and an area to be scanned aloneis irradiated with laser light. The AO modulator is desirably formed ofa material which can block laser light and which is not deformed ordamaged by laser light.

[0195]FIG. 18B shows an example of the relation between the shape of amask for patterning a semiconductor film and an area to be irradiatedwith laser light. Indicated by 570 is the shape of a mask for patterninga semiconductor film. A semiconductor film is patterned in accordancewith the mask after the semiconductor film is crystallized by laserirradiation.

[0196] Denoted by 571 is an area irradiated with laser light. An areasurrounded by the dashed line is not irradiated with laser light becausean AO modulator changes the direction of laser light to block the laserlight. In this embodiment, an area where crystallization is unnecessaryis not irradiated with laser light, or even if irradiated, laser lightused is low in energy density. Therefore, damage to a substrate which iscaused by irradiating an area that does not need irradiation with laserlight can be further reduced.

[0197] Next, a description is given on a process of manufacturing asemiconductor device having a pixel portion, a signal line drivingcircuit, and a scanning line driving circuit, in which an AO modulatoris used for selective laser light irradiation of the pixel portion, thesignal line driving circuit, and the scanning line driving circuit toirradiate each of them once.

[0198] First, as shown in FIG. 19A, laser light runs over a signal linedriving circuit 302 and a pixel portion 301 in the direction indicatedby the arrow for laser light irradiation. At this point, instead ofirradiating the entire surface of the substrate with laser light, an AOmodulator is used to change the direction of laser light and block thelaser light so that a scanning line driving circuit 303 is notirradiated with laser light.

[0199] Then, as shown in FIG. 19B, the scanning line driving circuit 303is irradiated with laser light by running laser light over the scanningline driving circuit 303 in the direction indicated by the arrow. Atthis time, the signal line driving circuit 302 and the pixel portion 301are not irradiated with laser light.

[0200] The description given next is about another example of using anAO modulator for selective laser light irradiation of a pixel portion, asignal line driving circuit, and a scanning line driving circuit toirradiate each of them once.

[0201] First, as shown in FIG. 19C, laser light runs over the scanningline driving circuit 303 and a pixel portion 301 in the directionindicated by the arrow for laser light irradiation. At this point,instead of irradiating the entire surface of the substrate with laserlight, an AO modulator is used to change the direction of laser lightand block the laser light so that the signal line driving circuit 302 isnot irradiated with laser light.

[0202] Then, as shown in FIG. 19D, the signal line driving circuit 302is irradiated with laser light by running laser light over the signalline driving circuit 302 in the direction indicated by the arrow. Duringthis, the scanning line driving circuit 303 and the pixel portion 301are not irradiated with laser light.

[0203] As described above, using an AO modulator makes selective laserirradiation possible and therefore the laser light scanning directioncan be changed for each circuit in accordance with layout of channelformation regions in active layers of the respective circuits. Sinceirradiating the same circuit with laser light twice can be avoided, iteliminates limitations in laser light path setting and active layerlayout which are for preventing edges of second time laser light fromoverlapping active layers laid out.

[0204] Next, an example is described in which plural panels aremanufactured from a large-sized substrate when an AO modulator is usedfor selective laser light irradiation of a pixel portion, a signal linedriving circuit, and a scanning line driving circuit to irradiate eachof them once.

[0205] First, as shown in FIG. 20, laser light runs over a signal linedriving circuit 382 and pixel portion 381 of each panel in the directionindicated by the arrow for laser light irradiation. At this point,instead of irradiating the entire surface of the substrate with laserlight, an AO modulator is used to change the direction of laser lightand block the laser light so that a scanning line driving circuit 383 isnot irradiated with laser light.

[0206] Then, the scanning line driving circuit 383 of each panel isirradiated with laser light by running laser light over the scanningline driving circuit 383 in the direction indicated by the arrow. Atthis time, the signal line driving circuit 382 and the pixel portion 381are not irradiated with laser light. Denoted by 385 is a scrub line of asubstrate 386.

[0207] This embodiment can be combined with Embodiment 1.

[0208] Embodiment 3

[0209] This embodiment describes, in relation to the energy density, thedistance between centers of beam spots when they are overlapped.

[0210] In FIG. 21, the energy density distribution in the central axisdirection of each beam spot is indicated by the solid line and theenergy density distribution of the synthesized beam spot is indicated bythe dashed line. The energy density value in the central axis directionof a beam spot generally follows Gaussian distribution.

[0211] Assume that, before synthesization, the distance in the centralaxis direction of a beam spot where the energy density is equal to ormore than the peak value, 1/e², is 1. Then, the distance between peaksis given as X. An increase from the peak value of the average valleyvalue to the peak value after synthesization is given as Y. The relationbetween X and Y obtained through simulation is shown in FIG. 38. Y inFIG. 38 is expressed as a percentage.

[0212] In FIG. 38, the energy difference Y is expressed by the followingExpression 1, which is an approximate expression.

[0213] [Expression 1]

Y=60−293X+340X ² (X is the larger one of two solutions.)

[0214] According to Expression 1, if energy difference is desired to be,for example, around 5%, X≅0.584 has to be satisfied. Ideally, Y=0 butthis makes the length of the beam spot short. Therefore, X is preferablydetermined balancing it with throughput.

[0215] The acceptable range of Y is described next. FIG. 39 shows theoutput (W) distribution of a YVO₄ laser in relation to the beam width inthe central axis direction when a beam spot has an elliptical shape. Ahatched region is the range of an energy output necessary to obtainsatisfactory crystallinity. The graph shows that it is sufficient if theoutput energy of synthesized laser light falls between 3.5 W and 6 W.

[0216] The energy difference Y for obtaining satisfactory crystallinityreaches its maximum when the maximum value and minimum value of theoutput energy of the synthesized beam spot fall within the range of anenergy output necessary to obtain satisfactory crystallinity such thatthe values closely match the upper limit and lower limit of the range,respectively. Therefore, in the case of FIG. 39, satisfactorycrystallinity is obtained if the energy difference Y is ±26.3%.

[0217] The range of an energy output necessary to obtain satisfactorycrystallinity is varied depending on which level of crystallinity isdeemed as satisfactory, and the output energy distribution is alsovaried depending on the beam spot shape. Accordingly, the acceptablerange of the energy difference Y is not limited to the values describedabove. It is necessary for a designer to determine the range of anenergy output necessary to obtain satisfactory crystallinity and to setthe acceptable range of the energy difference Y from the output energydistribution of the laser light used.

[0218] This embodiment can be combined with Embodiment 1 or 2.

[0219] Embodiment 4

[0220] This embodiment describes how beam spots are overlapped. FIGS.22A to 22C show beam spots before synthesization and their regions wherethe energy density is the peak energy density multiplied by 1/e².

[0221]FIG. 22A shows a case in which four beam spots are overlappedwhile avoiding overlap of the center of one beam spot and the center ofanother beam spot.

[0222]FIG. 22B shows a case in which four beam spots are overlapped withthe center of one beam spot overlapping an edge of another beam spot.

[0223]FIG. 22C shows a case of overlapping four beam spots such that thecenter of one beam spot overlaps an edge of a beam spot next to a beamspot that is adjacent to the one beam spot.

[0224] The present invention is not limited to these structures. Howbeam spots are overlapped can be determined at designer's discretion.This embodiment can be combined with Embodiments 1 through 3.

[0225] Embodiment 5

[0226] This embodiment gives a description with reference to FIGS. 23Ato 26 on a method of manufacturing an active matrix substrate using alaser crystallization method of the present invention. In thisspecification, a substrate on which a CMOS circuit, a driving circuit,and a pixel portion that has a pixel TFT and capacitor storage are allformed is called an active matrix substrate for conveniences' sake.

[0227] This embodiment uses glass such as barium borosilicate glass oraluminoborosilicate glass to form a substrate 600. Instead of glass, thesubstrate 600 may be a quartz substrate, silicon substrate, metalsubstrate, or stainless steel substrate with an insulating film formedon its surface. A plastic substrate may also be employed if it hasenough heat resistance to withstand the processing temperature.

[0228] On the substrate 600, an insulating film such as a silicon oxidefilm, a silicon nitride film, or a silicon oxynitride film is formed asa base film 601 by a known method (sputtering, LPCVD, plasma CVD, or thelike). The base film 601 in this embodiment consists of two layers, basefilms 601a and 601b. However, the base film 601 may be a single layer orthree or more layers of the insulating films listed in the above (FIG.23A).

[0229] Next, an amorphous semiconductor film 692 is formed on the basefilm 601 by a known method (sputtering, LPCVD, plasma CVD, or the like)to a thickness of 25 to 80 nm (preferably 30 to 60 nm) (FIG. 23B).Although an amorphous semiconductor film is formed in this embodiment, amicrocrystalline semiconductor film or a crystalline semiconductor filmmay be formed instead. A compound semiconductor film having an amorphousstructure, such as an amorphous silicon germanium film, may also beemployed.

[0230] Next, the amorphous semiconductor film 692 is patterned andetched by anisotropic dry etching in an atmosphere containing halogenfluoride, for example, ClF, ClF₃, BrF, BrF₃, IF, or IF₃, to formsub-islands 693 a, 693 b, and 693 c.

[0231] The sub-islands 693 a, 693 b, and 693 c are crystallized by lasercrystallization. This laser crystallization employs a laser irradiationmethod of the present invention. Specifically, the sub-islands 693 a,693 b, and 693 c are selectively irradiated with laser light inaccordance with mask information inputted to a computer of laserirradiation apparatus. Instead of crystallizing the sub-islands by lasercrystallization alone, other known crystallization methods (such as RTA,thermal crystallization using an annealing furnace, or thermalcrystallization using a metal element that promotes crystallization) maybe used in combination with laser crystallization.

[0232] If the amorphous semiconductor film is crystallized by acontinuous wave solid-state laser using the second to fourth harmonic ofthe fundamental wave thereof, crystals of large grain size can beobtained. Typically, the second harmonic (532 nm) or third harmonic (355nm) of a Nd:YVO₄ laser (fundamental wave: 1064 nm) is desirablyemployed. To be specific, laser light emitted from a continuous waveYVO₄ laser is converted into harmonic by a non-linear optical element toobtain laser light with output of 10 W. Alternatively, harmonic isobtained by putting a YVO₄ crystal and a non-linear optical element in aresonator. The harmonic is preferably shaped into oblong or ellipticallaser light on an irradiation surface by an optical system and thenirradiates a processing object. The energy density required at thispoint is around 0.01 to 100 MW /cm² (preferably 0.1 to 10 MW /cm²).During the irradiation, the semiconductor film is moved relative to thelaser light at a rate of about 10 to 2000 cm/s.

[0233] For laser irradiation, a pulse oscillation or continuous wave gaslaser or solid-state laser can be employed. Examples of the gas laserinclude an excimer laser, an Ar laser, and a Kr laser. Examples of thesolid-state laser include a YAG laser, a YVO₄ laser, a YLF laser, aYAlO₃ laser, a glass laser, a ruby laser, an alexandrite laser, a Ti:sapphire laser, and a Y₂O₃ laser. The solid-state laser employed may bea laser that uses crystals of YAG, YVO₄, YLF, YAlO₃ or the like dopedwith Cr, Nd, Er, Ho, Ce, Co, Ti, Yb, or Tm. The fundamental wave of thelaser is varied depending on the material used for doping but laserlight obtained has a fundamental wave of about 1 μm. A non-linearoptical element is used to obtain harmonic of the fundamental wave.

[0234] Through the above laser crystallization, the sub-islands 693 a,693 b, and 693 c are irradiated with laser light and sub-islands 694 a,694 b, and 694 c with improved crystallinity are formed (FIG. 23B).

[0235] The sub-islands 694 a, 694 b, and 694 c with improvedcrystallinity are patterned into desired shapes to form crystallizedislands 602 to 606 (FIG. 23C).

[0236] After the islands 602 to 606 are formed, the islands may be dopedwith a minute amount of impurity element (boron or phosphorus) in orderto control the threshold of TFTs.

[0237] Then a gate insulating film 607 is formed to cover the islands602 to 606. The gate insulating film is an insulating film containingsilicon and is formed by plasma CVD or sputtering to a thickness of 40to 150 nm. In this embodiment, a silicon oxynitride film (compositionratio: Si=32%, O=59%, N=7%, H=2%) is formed by plasma CVD to a thicknessof 110 nm. The gate insulating film is not limited to the siliconoxynitride film, and a single layer or laminate of other insulatingfilms containing silicon may also be employed.

[0238] If a silicon oxide film is chosen for the gate insulating film,it is formed by plasma CVD in which TEOS (tetraethyl orthosilicate) andO₂ are mixed, the reaction pressure is set to 40 Pa, the substratetemperature to 300 to 400° C., and the high frequency (13.56 MHz) powerdensity to 0.5 to 0.8 W/cm² for electric discharge. The thus formedsilicon oxide film can provide excellent characteristics as a gateinsulating film if it subsequently receives thermal annealing at 400 to500° C.

[0239] Next, a laminate of a first conductive film 608 with a thicknessof 20 to 100 nm and a second conductive film 609 with a thickness of 100to 400 nm is formed on the gate insulating film 607. In this embodiment,a TaN film with a thickness of 30 nm is formed as the first conductivefilm 608 and then a W film with a thickness of 370 nm is laid thereon asthe second conductive film 609. The TaN film is formed by sputteringwith Ta as the target in an atmosphere containing nitrogen. The W filmis formed by sputtering using a W target.

[0240] The W film may instead be formed by thermal CVD using tungstenhexafluoride (WF₆). In either case, the W film has to have lowresistivity in order to use it as a gate electrode. Desirably, the Wfilm has a resistivity of 20 μΩcm or less. The resistivity of the W filmcan be lowered by increasing the grain size. However, if too manyimpurity elements such as oxygen are contained in the W film,crystallization is hindered to raise the resistivity. Accordingly, thisembodiment uses sputtering with W of high purity (purity: 99.9999%) asthe target to form the W film taking care not to allow impurities fromthe air to mix in the film during its formation. As a result, the W filmcan have a resistivity of 9 to 20 μΩcm.

[0241] Although the first conductive film 608 and the second conductivefilm 609 in this embodiment are a TaN film and a W film, respectively,there is no particular limitation thereto. The first conductive film andsecond conductive film each can be formed from an element selected fromthe group consisting of Ta, W, Ti, Mo, Al, Cu, Cr, and Nd, or an alloyor compound mainly containing the above elements. Alternatively, thefirst conductive film and the second conductive film may besemiconductor films, typically polycrystalline silicon films, doped withphosphorus or other impurity elements or may be Ag—Pd—Cu alloy films.The following combinations are also employable: a combination of atantalum (Ta) film as the first conductive film and a W film as thesecond conductive film, a combination of a titanium nitride (TiN) filmas the first conductive film and a W film as the second conductive film,a combination of a tantalum nitride (TaN) film as the first conductivefilm and a W film as the second conductive film, a combination of atantalum nitride (TaN) film as the first conductive film and an Al filmas the second conductive film, and a combination of a tantalum nitride(TaN) film as the first conductive film and a Cu film as the secondconductive film.

[0242] The present invention is not limited to a two-layer structureconductive film. For example, a three-layer structure consisting of atungsten film, aluminum-silicon alloy (Al—Si) film, and titanium nitridefilm layered in this order may be employed. When the three-layerstructure is employed, the tungsten film may be replaced by a tungstennitride film, the aluminum-silicon alloy (Al—Si) film may be replaced byan aluminum-titanium alloy (Al—Ti) film, and the titanium nitride filmmay be replaced by a titanium film.

[0243] It is important to select the optimum etching method and etchantfor the conductive film material employed.

[0244] Next, resist masks 610 to 615 are formed by photolithography andthe first etching treatment is conducted in order to form electrodes andwirings. The first etching treatment employs first and second etchingconditions (FIG. 24B). In this embodiment, the first etching conditionsinclude employing ICP (inductively coupled plasma) etching, using CF₄,Cl₂, and O₂ as etching gas, setting the gas flow rate ratio thereof to25:25:10 (seem), and applying an RF (13.56 MHz) power of 500 W to acoiled electrode at a pressure of 1 Pa to generate plasma for etching.The substrate side (sample stage) also receives an RF (13.56 MHz) powerof 150 W to apply a substantially negative self-bias voltage. The W filmis etched under these first etching conditions to taper the firstconductive layer around the edges.

[0245] Thereafter, the first etching conditions are switched to thesecond etching conditions without removing the resist masks 605 to 615.The second etching conditions include using CF₄ and Cl₂ as etching gas,setting the gas flow rate ratio thereof to 30:30 (sccm), and giving anRF (13.56 MHz) power of 500 W to a coiled electrode at a pressure of 1Pa to generate plasma for etching for about 30 seconds. The substrateside (sample stage) also receives an RF power (13.56 MHz) of 20 W toapply a substantially negative self-bias voltage. Under the secondetching conditions where a mixture of CF₄ and Cl₂ is used, the W filmand the TaN film are etched to the same degree. In order to etch thefilms without leaving any residue on the gate insulating film, theetching time is increased by around 10 to 20%.

[0246] In the first etching treatment, the first conductive layer andthe second conductive layer are tapered around their edges by the effectof the bias voltage applied to the substrate side if the resist maskshave appropriate shapes. The angle of the tapered portions is 15 to 45°.In this way, first shape conductive layers 617 to 622 consisting of thefirst conductive layer and the second conductive layer (first conductivelayers 617 a to 622 a and second conductive layers 617 b to 622 b) areformed through the first etching treatment. Denoted by 616 is a gateinsulating film, and regions of the gate insulating film that are notcovered with the first shape conductive layers 617 to 622 are etched andthinned by about 20 to 50 nm.

[0247] Next follows the second etching treatment with the resist maskskept in place (FIG. 24C). Here, CF₄, Cl₂ and O₂ are used as etching gasto etch the W film selectively. Second conductive layers 628 b to 633 bare formed through the second etching treatment. On the other hand, thefirst conductive layers 617 a to 622 a are hardly etched in thistreatment and second shape conductive layers 628 to 633 are formed.

[0248] Without removing the resist masks, the first doping treatment isconducted to dope the islands with an impurity element that gives then-type conductivity in low concentration. The doping treatment employsion doping or ion implantation. The ion doping conditions includesetting the dose to 1×10¹³ to 5×10¹⁴ atoms/cm² and the accelerationvoltage to 40 to 80 kV. In this embodiment, the dose is set to 1.5×10¹³atoms/cm² and the acceleration voltage is set to 60 kV. An impurityelement that gives the n-type conductivity is an element belonging toGroup 15, typically, phosphorus (P) or arsenic (As). This embodimentemploys phosphorus (P). In this case, the conductive layers 628 to 633serve as masks against the impurity element that gives the n-typeconductivity and impurity regions 623 to 627 are formed in aself-aligning manner. The impurity regions 623 to 627 are doped with theimpurity element that gives the n-type conductivity in a concentrationof 1×10¹⁸ to 1×10²⁰ /cm³.

[0249] The resist masks are removed and new resist masks 634 a to 634 care formed for the second doping treatment. The acceleration voltage ishigher in the second doping treatment than in the first dopingtreatment. The ion doping conditions include setting the dose to 1×10¹³to 1×10¹⁵ atoms/cm² and the acceleration voltage to 60 to 120 kV. In thesecond doping treatment, the second conductive layers 628 b to 632 b areused as masks against the impurity element and the islands under thetapered portions of the first conductive layers are doped with theimpurity element. Then, the third doping treatment is carried out withthe acceleration voltage set lower than that in the second dopingtreatment to obtain the state of FIG. 25A. The ion doping conditionsinclude setting the dose to 1×10¹⁵ to 1×10¹⁷ atoms/cm² and theacceleration voltage to 50 to 100 kV. As a result of the second andthird doping treatments, low concentration impurity regions 636, 642,and 648 overlapping the first conductive layers are doped with animpurity element that gives the n-type conductivity in a concentrationof 1×10¹⁸ to 5×10¹⁹/cm³, and high concentration impurity regions 635,641, 644, and 647 are doped with an impurity element that gives then-type conductivity in a concentration of 1×10¹⁹ to 5×10^(2l)/cm³.

[0250] If the acceleration voltage is suitably set, the second dopingtreatment and the third doping treatment can be integrated, so that thelow concentration impurity regions and high concentration impurityregions are formed in one doping treatment.

[0251] Next, the resist masks are removed and new resist masks 650 a to650 c are formed for the fourth doping treatment. Through the fourthdoping treatment, impurity regions 653, 654, 659, and 660 are formed inthe islands that are to serve as active layers of p-channel TFTs. Theimpurity regions 653, 654, 659, and 660 are doped with an impurityelement that gives the conductivity reverse to the n-type conductivity.In the fourth doping treatment, the second conductive layers 628 a to632 a are used as masks against the impurity element. In this way, theimpurity regions doped with an impurity element that gives the p-typeconductivity are formed in a self-aligning manner. The impurity regions653, 654, 659 and 660 in this embodiment are formed by ion doping usingdiborane (B₂H₆) (FIG. 25B). In the fourth doping treatment, the islandsfor forming n-channel TFTs are covered with the resist masks 650 a to650 c. The impurity regions 653, 654, 659, and 660 have been doped withphosphorus by the first through the third doping treatment in differentconcentrations. However, any of the impurity regions is doped in thefourth doping treatment with an impurity element that gives the p-typeconductivity in a concentration of 1×10¹⁹ to 5×10²¹ atoms/cm².Therefore, the impurity regions have no problem in functioning as sourceregions and drain regions of p-channel TFTs.

[0252] Through the above steps, impurity regions are formed in therespective islands.

[0253] Next, the resist masks 650 a to 650 c are removed and a firstinterlayer insulating film 661 is formed. This first interlayerinsulating film 661 is an insulating film containing silicon and isformed by plasma CVD or sputtering to a thickness of 100 to 200 nm. Inthis embodiment, a silicon oxynitride film is formed by plasma CVD to athickness of 150 nm. The first interlayer insulating film 661 is notlimited to the silicon oxynitride film but may be a single layer orlaminate of other insulating films containing silicon.

[0254] Next, a laser irradiation method is used as shown in FIG. 25C foractivation treatment. If laser annealing is chosen, the laser that hasbeen used in crystallization can be employed. In activation, themobility is set to the same level as the mobility in crystallization andthe energy density required is 0.01 to 100 MW/cm² (preferably 0.01 to 10MW/cm²). It is also possible to use a continuous wave laser incrystallization and a pulse oscillation laser in activation.

[0255] The activation treatment may be conducted before the firstinterlayer insulating film is formed.

[0256] Then, thermal processing (heat treatment at 300 to 550° C. for 1to 12 hours) is conducted for hydrogenation. This step is to terminatedangling bonds in the islands using hydrogen that is contained in thefirst interlayer insulating film 661. Examples of alternativehydrogenation means include plasma hydrogenation using hydrogen that isexcited by plasma, and heat treatment conducted in an atmosphere whichcontains 3 to 100% of hydrogen at 300 to 650° C. for 1 to 12 hours. Inthis case, the semiconductor layers can be hydrogenated irrespective ofpresence or absence of the first interlayer insulating film.

[0257] On the first interlayer insulating film 661, a second interlayerinsulating film 662 is formed from an inorganic insulating material oran organic insulating material. In this embodiment, an acrylic resinfilm is formed to a thickness of 1.6 μm. Next, a third interlayerinsulating film 672 is formed after the formation of the secondinterlayer insulating film 662 so as to come into contact with thesecond interlayer insulating film 662.

[0258] Subsequently, wirings 663 to 668 are formed to be electricallyconnected to the respective impurity regions in a driving circuit 686.These wirings are formed by patterning a laminate of a 50 nm thick Tifilm and 500 nm thick alloy film (Al—Ti alloy film). The wirings are notlimited to the two-layer structure and may take a single-layer structureor a multi-layer structure with three or more layers. Wiring materialsare not limited to Al and Ti. For example, the wirings may be formed bypatterning a laminate film in which an Al film or a Cu film is formed ona TaN film and a Ti film is formed thereon (FIG. 26).

[0259] In a pixel portion 687, a pixel electrode 670, a gate wiring 669,and a connection electrode 668 are formed. The connection electrode 668allows source wirings (a laminate of 643 a and 643 b) to electricallyconnect with a pixel TFT. The gate wiring 669 forms an electricalconnection with a gate electrode of the pixel TFT. The pixel electrode670 forms an electrical connection with a drain region 690 of the pixelTFT and another electrical connection with an island 685 that functionsas one of electrodes constituting capacitor storage. In this patentapplication, the pixel electrode and the connection electrode are formedfrom the same material. Desirably, the pixel electrode 670 is formedfrom a material having excellent reflectivity, for example, a filmmainly containing Al or Ag, or a laminate of such films.

[0260] The driving circuit 686, which has a CMOS circuit composed of ann-channel TFT 681 and a p-channel TFT 682 and has an n-channel TFT 683,and the pixel portion 687, which has a pixel TFT 684 and capacitorstorage 685, can thus be formed on the same substrate. In this way, anactive matrix substrate is completed.

[0261] The n-channel TFT 681 of the driving circuit 686 has a channelformation region 637, the low concentration impurity regions 636 (GOLD(gate overlapped LDD) region), and high concentration impurity regions652. The low concentration impurity regions 636 overlap the firstconductive layer 628 a that constitutes a part of a gate electrode. Oneof the high concentration impurity regions 652 serves as a source regionand the other serves as a drain region. Connected to this n-channel TFT681 through an electrode 666 to form the CMOS circuit is the p-channelTFT 682. The p-channel TFT 682 has a channel formation region 640, thehigh concentration impurity regions 653, and the impurity regions 654.One of the high concentration impurity regions 653 serves as a sourceregion and the other serves as a drain region. The impurity regions 654have introduced therein an impurity element that gives the p-typeconductivity. The n-channel TFT 683 has a channel formation region 643,the low concentration impurity regions 642 (GOLD regions), and highconcentration impurity regions 656. The low concentration impurityregions 642 overlap the first conductive layer 630a that constitutes apart of a gate electrode. One of the high concentration impurity regions656 serves as a source region and the other serves as a drain region.

[0262] The pixel TFT 684 of the pixel portion has a channel formationregion 646, the low concentration impurity regions 645 (LDD regions),and high concentration impurity regions 658. The low concentrationimpurity regions 645 are formed outside of the gate electrode. One ofthe high concentration impurity regions 658 serves as a source regionand the other serves as a drain region. The island that serves as one ofelectrodes of the capacitor storage 685 is doped with an impurityelement that gives the n-type conductivity and an impurity element thatgives the p-type conductivity. The capacitor storage 685 is composed ofan electrode (a laminate of 632 a and 632 b) and an island with theinsulating film 616 as dielectric.

[0263] According to the pixel structure of this embodiment, edges of apixel electrode overlap a source wiring so that the gap between pixelelectrodes is shielded against light without using a black matrix.

[0264] This embodiment can be combined with Embodiments 1 through 4.

[0265] Embodiment 6

[0266] This embodiment describes a process of manufacturing a reflectiveliquid crystal display device from the active matrix substrate that ismanufactured in Embodiment 5. The description is given with reference toFIG. 27.

[0267] First, an active matrix substrate in the state of FIG. 26 isobtained following the description in Embodiment 5. On the active matrixsubstrate of FIG. 26, at least on the pixel electrode 670, anorientation film 867 is formed and subjected to rubbing treatment. Inthis embodiment, before forming the orientation film 867, an acrylicresin film or other organic resin film is patterned to form in desiredpositions columnar spacers 872 for keeping the gap between substrates.Instead of the columnar spacers, spherical spacers may be sprayed ontothe entire surface of the substrate.

[0268] Next, an opposite substrate 869 is prepared. Colored layers 870and 871 and a planarization film 873 are formed on the oppositesubstrate 869. The red colored layer 870 and the blue colored layer 871are overlapped to form a light-shielding portion. Alternatively, a redcolored layer and a green colored layer may be partially overlapped toform a light-shielding portion.

[0269] This embodiment uses the substrate shown in Embodiment 5.Therefore, at least the gap between the gate wiring 669 and the pixelelectrode 670, the gap between the gate wiring 669 and the connectionelectrode 668, and the gap between the connection electrode 668 and thepixel electrode 670 have to be shielded against light. In thisembodiment, the colored layers are arranged such that thelight-shielding portion that is a laminate of the colored layersoverlaps these gaps to be shielded against light. Then, the oppositesubstrate is bonded.

[0270] The number of steps is thus reduced by using a light-shieldingportion that is a laminate of colored layers to shield gaps betweenpixels against light instead of forming a light-shielding layer such asa black mask.

[0271] Next, a transparent conductive film is formed as an oppositeelectrode 876 on the planarization film 873 at least in the pixelportion. An orientation film 874 is formed on the entire surface of theopposite substrate and is subjected to rubbing treatment.

[0272] Then, the opposite substrate is bonded by a seal member 868 tothe active matrix substrate on which the pixel portion and the drivingcircuit are formed. The seal member 868 has fillers mixed therein, andthe fillers together with the columnar spacers keep the gap uniformbetween the two substrates while they are bonded. Thereafter, a liquidcrystal material 875 is injected to the space between the two substratesand the device is completely sealed with a sealing agent (not shown inthe drawing). The liquid crystal material 875 is a known liquid crystalmaterial. In this way, a reflective liquid crystal display device shownin FIG. 27 is completed. If necessary, the active matrix substrate orthe opposite substrate is cut into pieces of desired shapes. Apolarizing plate (not shown in the drawing) is then bonded to theopposite substrate alone. Thereafter, an FPC is bonded by a knowntechnique.

[0273] The thus manufactured liquid crystal display device has TFTsformed from a semiconductor film that has crystal grains of large grainsize formed through irradiation by laser light with periodic or uniformenergy distribution. This gives the liquid crystal display devicesatisfactory operation characteristics and reliability. Such liquidcrystal display device can be used as a display unit of variouselectronic equipment.

[0274] This embodiment can be combined with Embodiments 1 through 5.

[0275] Embodiment 7

[0276] This embodiment describes an example of manufacturing a lightemitting device using the TFT manufacturing method when manufacturingthe active matrix substrate shown in Embodiment 5. “Light emittingdevice” is a generic term for a display panel in which a light emittingelement is formed on a substrate and sealed between the substrate and acover member, and for a display module obtained by mounting a TFT andthe like to the display panel. A light emitting element has a layercontaining an organic compound that provides luminescence uponapplication of electric field (electroluminescence), as well as an anodelayer and a cathode layer. Luminescence obtained from organic compoundsis classified into light emission upon return to the base state fromsinglet excitation (fluorescence) and light emission upon return to thebase state from triplet excitation (phosphorescence). The presentinvention includes one or both of the two types of light emission.

[0277] In this specification, all the layers that are formed between acathode and an anode in a light emitting element are collectivelydefined as an organic light emitting layer. Specifically, an organiclight emitting layer includes a light emitting layer, a hole injectionlayer, an electron injection layer, a hole transporting layer, anelectron transporting layer, etc. The basic structure of a lightemitting element is a laminate of an anode layer, light emitting layer,and cathode layer layered in this order. The basic structure may bemodified into a laminate in which an anode layer, a hole injectionlayer, a light emitting layer, a cathode layer, etc. are layered in thisorder, or a laminate in which an anode layer, a hole injection layer, alight emitting layer, an electron transporting layer, a cathode layer,etc. are layered in this order.

[0278] A light emitting element used in this embodiment may also take amode in which a hole injection layer, an electron injection layer, ahole transporting layer, or an electron transporting layer is formedsolely of an inorganic compound or from a material obtained by mixing aninorganic compound with an organic compound. The layers listed may bepartially mixed with one another.

[0279]FIG. 28A is a sectional view of a light emitting device of thisembodiment where manufacturing process is finished up through formationof a third interlayer insulating film 750. In FIG. 28A, a switching TFT733 and a current controlling TFT 734 on a substrate 700 are formed bythe manufacturing method of Embodiment 5. The switching TFT 733 in thisembodiment has a double gate structure in which two channel formationregions are formed. However, the switching TFT 733 may take a singlegate structure having one channel formation region or a structure havingthree or more channel formation regions. The current controlling TFT 734in this embodiment has a single gate structure in which one channelformation region is formed, but it may take a structure having two ormore channel formation regions.

[0280] An n-channel TFT 731 and p-channel TFT 732 of a driving circuiton the substrate 700 are formed by the manufacturing method ofEmbodiment 5. The TFTs have a single gate structure in this embodiment,but may take a double gate structure or a triple gate structure.

[0281] The third interlayer insulating film 750 is, in a light emittingdevice, effective in preventing moisture contained in a secondinterlayer insulating film 751 from entering an organic light emittinglayer. When the second interlayer insulating film 751 has an organicresin material, forming the third interlayer insulating film 750 isparticularly effective since organic resin materials contain a lot ofmoisture.

[0282] After the process of Embodiment 5 is finished up through the stepof forming the third interlayer insulating film, a pixel electrode 711is formed on the third interlayer insulating film 750 in thisembodiment.

[0283] The pixel electrode 711 is a pixel electrode formed from atransparent conductive film (an anode of a light emitting element). Thetransparent conductive film used may be formed from a compound of indiumoxide and tin oxide or a compound of indium oxide and zinc oxide, orfrom zinc oxide alone, tin oxide alone, or indium oxide alone. Thetransparent conductive film doped with gallium may be used. The pixelelectrode 711 is formed on the flat third interlayer insulating film 750before wirings are formed. In this embodiment, it is very important touse a second interlayer insulating film 751 formed of a resin to levelthe level differences caused by the TFTs. If there are leveldifferences, they may cause defective light emission since a lightemitting layer which is formed later is very thin. Accordingly, thesurface should be leveled before the pixel electrode is formed, so thatthe light emitting layer can be formed on as flat a surface as possible.

[0284] Next, as shown in FIG. 28B, a resin film dispersed with blackdye, carbon, or black pigments is formed so as to cover the thirdinterlayer insulating film 750. An opening is formed in the film at aposition where a light emitting element is formed. This film serves as alight-shielding film 770. The material of the resin film is typicallypolyimide, polyamide, acrylic, or BCB (benzocyclobutene), but is notlimited thereto. Examples of other light-shielding film materials thanorganic resins include silicon, silicon oxide, silicon oxynitride, andthe like with black dye, carbon, or black pigments mixed therein. Thelight-shielding film 770 has an effect of preventing external lightreflected by wirings 701 to 707 from reaching eyes of a viewer.

[0285] After the pixel electrode 711 is formed, contact holes are formedin a gate insulating film 752, a first interlayer insulating film 753,the second interlayer insulating film 751, the third interlayerinsulating film 750, and the light-shielding film 770. Then a conductivefilm is formed on the light-shielding film 770 to cover the pixelelectrode 711. The conductive film is etched to form wirings 701 to 707that are electrically connected to impurity regions of the respectiveTFTs. These wirings are formed by patterning a laminate of a 50 nm thickTi film and 500 nm thick alloy film (an alloy of Al and Ti). The wiringsare not limited to the two-layer structure and may take a single-layerstructure or a multi-layer structure of three or more layers. Wiringmaterials are not limited to Al and Ti. For example, the wirings may beformed by patterning a laminate film in which an Al film or a Cu film isformed on a TaN film and a Ti film is formed thereon (FIG. 28A).

[0286] The wiring 707 is a source wiring (corresponding to a currentsupply line) of the current controlling TFT. The wiring 706 is anelectrode that electrically connects a drain region of the currentcontrolling TFT with the pixel electrode 711.

[0287] After the wirings 701 to 707 are formed, a bank 712 is formedfrom a resin material.

[0288] The bank 712 is formed by patterning acrylic film or polyimidefilm with a thickness of 1 to 2 μm so as to expose a part of the pixelelectrode 711.

[0289] A light emitting layer 713 is formed on the pixel electrode 711.Although only one pixel is shown in FIG. 28B, three types of lightemitting layers for R (red), G (green), and B (blue) colors are formedin this embodiment. The light emitting layers in this embodiment areformed by evaporation from low-molecular weight organic light emittingmaterials. Specifically, a copper phthalocyanine (CuPc) film with athickness of 20 nm is formed as a hole injection layer and atris-8-quinolinolate aluminum complex (Alq₃) film is layered thereon asa light emitting layer. The color of emitted light can be controlled bydoping Alq₃ with a fluorescent pigment such as quinacridon, perylene, orDCM1.

[0290] However, the materials given in the above are merely examples oforganic light emitting materials that can be used as light emittinglayers and there is no need to exclusively use them. A light emittinglayer (a layer in which carriers are moved to thereby emit light) isformed by freely combining a light emitting layer with an electriccharge transporting layer or an electric charge injection layer.Although a low-molecular weight organic light emitting material is usedfor a light emitting layer in the example shown in this embodiment, anintermediate-molecular weight organic light emitting material or ahigh-molecular weight organic light emitting material may be usedinstead. In this specification, an organic light emitting material withno sublimation property in which the number of molecules is 20 or lessand the length of molecular chain is 10 μm or less is called anintermediate-molecular weight organic light emitting material. As anexample of employing a high-molecular weight organic light emittingmaterial, a laminate structure may be adopted in which a polythiophene(PEDOT) film is formed as a hole injection layer by spin coating to athickness of 20 nm and a paraphenylene vinylene (PPV) film with athickness of about 100 nm is layered thereon as a light emitting layer.If a π-conjugate polymer of PPV is used, a light emission wavelengthranging from red to blue can be chosen. Inorganic materials such assilicon carbide can be used for an electric charge transporting layerand an electric charge injection layer. These organic light emittingmaterials and inorganic materials may be known materials.

[0291] Next, a cathode 714 is formed from a conductive film on the lightemitting layer 713. In this embodiment, the conductive film is a film ofan alloy of aluminum and lithium. A known MgAg film (a film of an alloyof magnesium and silver) may also be used. It is sufficient if thecathode material is a conductive film formed of an element that belongsto Group 1 or 2 in the periodic table or a conductive film doped withsuch element.

[0292] With formation of the cathode 714, a light emitting element 715is completed. The light emitting element 715 here refers to a diodecomposed of the pixel electrode (anode) 711, the light emitting layer713, and the cathode 714.

[0293] A protective film 754 may be provided so as to completely coverthe light emitting element 715. A carbon film or insulating filmsincluding a silicon nitride film and a silicon oxynitride film can beused for the protective film 754, which is a single layer or laminate ofthose films.

[0294] Preferably, a film with good coverage is used as the protectivefilm 754. A carbon film, especially DLC (diamond-like carbon) film iseffective. A DLC film can be formed at a temperature ranging from roomtemperature to 100° C. or less and therefore it is easy to form a DLCfilm above the light emitting layer 713, which has low heat resistance.Also, a DLC film has high oxygen blocking effect and is capable ofpreventing oxidization of the light emitting layer 713. Therefore, aproblem of the light emitting layer 713 being oxidized during thesubsequent sealing step can be avoided.

[0295] In this embodiment, the light emitting layer 713 is completelycovered with an inorganic insulating film such as a carbon film, asilicon nitride film, a silicon oxynitride film, an aluminum nitridefilm, or an aluminum oxynitride film, which serves well as a barrier.Therefore, degradation of the light emitting layer due to moisture,oxygen, and the like seeping into the light emitting layer can beprevented more effectively.

[0296] Prevention of the intrusion of impurities into the light emittinglayer becomes more thorough if silicon nitride films formed bysputtering with silicon as the target are used particularly for a thirdinsulating film 750, a passivation film 712, and the protective film754. The film formation conditions can be suitably chosen. Particularlypreferable conditions include using nitrogen (N₂) or a mixture gas ofnitrogen and argon as sputtering gas and applying a high-frequency powerfor sputtering. The substrate temperature is set to room temperature andno heating means is necessary. If an organic insulating film and anorganic compound layer have already been formed, it is desirable to formthe silicon nitride films without heating the substrate. However,heating in vacuum for several minutes to several hours at 50 to 100° C.for dehydrogenation treatment is preferable in order to thoroughlyremove adsorbed or occluded moisture.

[0297] Silicon nitride films formed from nitrogen gas alone bysputtering at room temperature using silicon as the target and applyinga 13.56 MHz high-frequency power are characterized in that theabsorption peaks of N—H bond and Si—H bond are not observed in itsinfrared absorption spectrum and neither is the absorption peak of Si—Obond, and the oxygen concentration and hydrogen concentration in thesesilicon nitride films are each 1 atomic % or less. This is another proofof effectiveness of the silicon nitride films in preventing theintrusion of impurities such as oxygen and moisture.

[0298] The light emitting element 715 is further covered with a sealingmember 717 and a cover member 718 is bonded thereto. A UV-curable resincan be used as the sealing member 717 and it is effective to put ahygroscopic material or antioxidant inside the sealing member. The covermember 718 used in this embodiment is a glass substrate, quartzsubstrate, or plastic substrate (or plastic film) with a carbon film(preferably diamond-like carbon film) formed on each side.

[0299] In this way, a light emitting device structured as shown in FIG.28B is completed. As to the steps following formation of the bank 712,it is effective to process in succession without exposing the device tothe air until after the protective film is formed. An advanced versionof this is to process in succession without exposing the device to theair until after the cover member 718 is bonded.

[0300] The n-channel TFTs 731 and 732, the switching TFT (n-channel TFT)733, and the current controlling TFT (n-channel TFT) 734 are thus formedon the substrate 700.

[0301] The light-shielding film 770 is formed between the thirdinterlayer insulating film 750 and the bank 712 in this embodiment.However, the present invention is not limited to this structure. Theimportant thing about placement of light-shielding film is that it hasto be placed in such a position that can prevent external lightreflected by the wirings 701 to 707 from reaching eyes of a viewer. Forinstance, if light emitted from the light emitting element 715 travelstoward the substrate 700 side as in this embodiment, the light-shieldingfilm may be placed between the first interlayer insulating film 753 andthe second interlayer insulating film 751. In this case also, thelight-shielding film has an opening to let light from the light emittingelement to pass therethrough.

[0302] As described with reference to FIGS. 28A and 28B, an n-channelTFT that is not easily degraded by the hot carrier effect can be formedby providing an impurity region that overlaps a gate electrode with aninsulating film sandwiched therebetween. Therefore, a highly reliablelight emitting device is obtained.

[0303] Although this embodiment shows the structures of the pixelportion and driving circuit alone, logic circuits such as a signaldivider circuit, a D/A converter, an operation amplifier, and a ycorrection circuit can be formed on the same insulator in addition tothe pixel portion and the driving circuit by following the manufacturingprocess of this embodiment. Furthermore, a memory and a microprocessorcan be formed on the same insulator.

[0304] The thus manufactured light emitting device has TFTs formed froma semiconductor film that has crystal grains of large grain size formedthrough irradiation by laser light with periodic or uniform energydistribution. This gives the light emitting device satisfactoryoperation characteristics and reliability. Such light emitting devicecan be used as a display unit of various electronic equipment.

[0305] Light emitted from the light emitting element travels toward theTFT side in this embodiment. Alternatively, light from the lightemitting element may travel in the opposite direction of the TFTs. Inthis case, a resin with black dye, carbon, or black pigments mixedtherein can be used for the bank. A sectional view of a light emittingdevice in which light emitted from a light emitting element travels inthe opposite direction of TFTs is shown in FIG. 33.

[0306] In FIG. 33, after a third interlayer insulating film 1950 isformed, contact holes are formed in a gate insulating film 1952, a firstinterlayer insulating film 1953, a second interlayer insulating film1951, and the third interlayer insulating film 1950. Then, a conductivefilm is formed on the third interlayer insulating film 1950 and isetched to form wirings 1901 to 1907 that are electrically connected toimpurity regions of the respective TFTs. These wirings are formed bypatterning an aluminum alloy film (an aluminum film containing 1 wt % oftitanium) with a thickness of 300 nm. The wirings are not limited to asingle-layer structure and may take a multi-layer structure having twoor more layers. Wiring materials are not limited to Al and Ti. A part ofthe wiring 1906 doubles as a pixel electrode.

[0307] After the wirings 1901 to 1907 are formed, a bank 1912 is formedfrom a resin material. The bank 1912 is formed by patterning a resinfilm with black dye, carbon, or black pigments mixed therein, having athickness of 1 to 2 μm so as to expose a part of the pixel electrode1906. The material of the resin film is typically polyimide, polyamide,acrylic, or BCB (benzocyclobutene), but is not limited thereto.

[0308] A light emitting layer 1913 is formed on the pixel electrode1906. Then, an opposite electrode (an anode of a light emitting element)is formed from a transparent conductive material to cover the lightemitting layer 1913. The transparent conductive film used may be formedfrom a compound of indium oxide and tin oxide or a compound of indiumoxide and zinc oxide, or from zinc oxide alone, tin oxide alone, orindium oxide alone. The transparent conductive film may be doped withgallium.

[0309] The pixel electrode 1906, the light emitting layer 1913, and anopposite electrode 1914 constitute a light emitting element 1915.

[0310] A light-shielding film 1970 has an effect of preventing externallight reflected by the wirings 1901 to 1907 from reaching eyes of aviewer.

[0311] This embodiment can be combined with any one of Embodiments 1through 6.

[0312] Embodiment 8

[0313] This embodiment describes the structure of a pixel in a lightemitting device that is one of semiconductor devices of the presentinvention. A sectional view of a pixel in a light emitting device ofthis embodiment is shown in FIG. 29.

[0314] In FIG. 29, 911 denotes a substrate and 912 denotes an insulatingfilm that serves as a base (hereinafter referred to as base film). Thesubstrate 911 is a light-transmissive substrate, typically, a glasssubstrate, a quartz substrate, a glass ceramic substrate, or acrystallized glass substrate. However, one that can withstand thehighest processing temperature of the manufacturing process has to bechosen.

[0315] Denoted by 8201 is a switching TFT that is an n-channel TFT and8202 is a current controlling TFT that is a p-channel TFT. When light isemitted from an organic light emitting layer toward the bottom face of asubstrate (the side where TFTs and the organic light emitting layer arenot formed), the above structure is preferred. However, the switchingTFT and the current controlling TFT each can assume both conductivitytypes and therefore 8201 may be a p-channel TFT and 8202 may be ann-channel TFT.

[0316] The switching TFT 8201 has an active layer, a gate insulatingfilm 918, gate electrodes 919 a and 919 b, a first interlayer insulatingfilm 920, a source signal line 921, and a drain wiring 922. The activelayer includes a source region 913, a drain region 914, LDD regions 915a to 915 d, a divider region 916 and channel formation regions 963 and964. The gate insulating film 918 or the first interlayer insulatingfilm 920 may be common to all TFTs on the substrate, or differentcircuits or elements may have different gate insulating films ordifferent first interlayer insulating films.

[0317] In the switching TFT 8201 shown in FIG. 29, the gate electrodes917 a and 917 b are electrically connected to each other to form adouble-gate structure. The switching TFT 8201 may take other multi-gatestructure (a structure including an active layer that has two or morechannel formation regions connected in series) than the double-gatestructure, such as a triple-gate structure.

[0318] A multi-gate structure is very effective in reducing OFF current.If OFF current of the switching TFT is lowered enough, the minimumcapacitance required for capacitor storage that is connected to a gateelectrode of the current controlling TFT 8202 can be reduced that much.In other words, it reduces the area of the capacitor storage. It istherefore effective to employ a multi-gate structure in increasing theeffective light emission area of a light emitting element.

[0319] Furthermore, the LDD regions 915 a to 915 d in the switching TFT8201 are placed so as to avoid overlap of the LDD regions and the gateelectrodes 919 a and 919 b with the gate insulating film 918 sandwichedtherebetween, and this structure is very effective in reducing OFFcurrent. The length (width) of each of the LDD regions 915 a to 915 d isset to 0.5 to 3.5 μm, typically, 2.0 to 2.5 μm. In a multi-gatestructure having two or more gate electrodes, the divider region 916 (aregion doped with the same impurity element in the same concentration asthe source region or the drain region) provided between the channelformation regions is effective in lowering OFF current.

[0320] The current controlling TFT 8202 has an active layer, the gateinsulating film 918, a gate electrode 930, the first interlayerinsulating film 920, a source signal line 931, and a drain wiring 932.The active layer includes a source region 926, a drain region 927, and achannel formation region 905. The current controlling TFT 8202 in thisembodiment is a p-channel TFT.

[0321] The drain region 914 of the switching TFT 8201 is connected tothe gate electrode 930 of the current controlling TFT 8202.Specifically, though not shown in the drawing, the gate electrode 930 ofthe current controlling TFT 8202 is electrically connected through thedrain wiring (also called a connection wiring) 922 to the drain region914 of the switching TFT 8201. The gate electrode 930 has a single gatestructure but may have a multi-gate structure. The source signal line931 of the current controlling TFT 8202 is connected to a power supplyline (not shown in the drawing).

[0322] The description given above is about the structures of the TFTsprovided in the pixel. At the same time the TFTs are formed, a drivingcircuit is also formed. Shown in FIG. 29 is a CMOS circuit that is thebasic unit constituting the driving circuit.

[0323] In FIG. 29A, a TFT structured to reduce hot carrier injectionwhile avoiding slowing the operation speed as much as possible is usedas an n-channel TFT 8204 of the CMOS circuit. The driving circuit hererefers to a source signal side driving circuit or a gate signal sidedriving circuit. Other logic circuits (such as a level shifter, an AIDconverter, and a signal divider circuit) may also be formed.

[0324] An active layer of the n-channel TFT 8204 of the CMOS circuitincludes a source region 935, a drain region 936, an LDD region 937, anda channel formation region 962. The LDD region 937 overlaps a gateelectrode 939 with the gate insulating film 918 sandwiched therebetween.

[0325] The LDD region 937 is formed only on the drain region 936 sidebecause it prevents slowing of the operation speed. In the n-channel TFT8204, the OFF current value is not so important and rather the operationspeed should be given priority. Accordingly, it is desirable if the LDDregion 937 overlaps the gate electrode completely to reduce theresistance component as much as possible. In other words, eliminatingoffset is preferred.

[0326] In a p-channel TFT 8205 of the CMOS circuit, degradation by hotcarrier injection is almost ignorable and therefore has no particularneed for an LDD region. Accordingly, its active layer includes a sourceregion 940, a drain region 941, and a channel formation region 961. Thegate insulating film 918 and a gate electrode 943 are provided under theactive layer. It is also possible for the p-channel TFT 8205 to have anLDD region as a countermeasure for hot carrier as in the n-channel TFT8204.

[0327] Denoted by 942, 938, 917 a, 917 b, and 929 are masks for formingthe channel formation regions 961 to 965.

[0328] The n-channel TFT 8204 and the p-channel TFT 8205 have abovetheir source regions a source signal line 944 and a source signal line945, respectively, with first interlayer insulating films 920 (or thefirst interlayer insulating film 920) sandwiched between the sourceregions and the source signal lines. The drain regions of the n-channelTFT 8204 and p-channel TFT 8205 are electrically connected to each otherby a drain wiring 946.

[0329] A laser irradiation method of the present invention can be usedin formation of the semiconductor film, crystallization of the activelayers, activation, and other steps where laser annealing is used.

[0330]FIG. 30 shows production flow for manufacturing the light emittingdevice of this embodiment. First, a semiconductor device is designedusing CAD. Specifically, a mask for an island is designed first and thena mask for a sub-island that includes one or more of such islands isdesigned.

[0331] Then, information concerning the shape of the designed mask for asub-island (pattern information) is inputted to a computer of laserirradiation apparatus. From the sub-island pattern information inputted,the computer calculates a width W_(S) of each sub-island in thedirection perpendicular to the scanning direction. Based on the widthW_(S) of each sub-island, a slit width W_(BW) in the directionperpendicular to the scanning direction is set. The laser light scanningpath is determined from the slit width W_(BW) with the position of amarker as the reference.

[0332] During this, a gate electrode is formed in accordance with themarker formed on a substrate. Alternatively, the gate electrode and themarker may be formed at the same time. Then a gate insulating film isformed so as to cover the gate electrode and a semiconductor film isformed so as to come into contact with the gate insulating film. Thesemiconductor film is patterned using the mask for a sub-island to forma sub-island. The substrate on which the sub-island is formed is set ona stage of the laser irradiation apparatus.

[0333] With the marker as the reference, laser light is irradiated alongthe set scanning path targeting the sub-island to crystallize thesub-island.

[0334] Thereafter, the sub-island having its crystallinity enhanced bythe laser light irradiation is patterned to form an island.Subsequently, a process of manufacturing a TFT from the island follows.Although specifics of the TFT manufacturing process are varied dependingon the TFT form, a typical process starts with forming an impurityregion in the island. Then an interlayer insulating film is formed so asto cover the island. A contact hole is formed in the interlayerinsulating film to partially expose the impurity region. A wiring isthen formed on the interlayer insulating film to reach the impurityregion through the contact hole.

[0335] The structure of this embodiment can be combined freely withEmbodiments 1 through 7.

[0336] Embodiment 9

[0337] This embodiment describes the structure of a pixel in a lightemitting device that is manufactured using a laser irradiation method ofthe present invention. A sectional view of a pixel in a light emittingdevice of this embodiment is shown in FIG. 31.

[0338] Denoted by 1751 is an n-channel TFT and 1752, a p-channel TFT.The n-channel TFT 1751 has a semiconductor film 1753, a first insulatingfilm 1770, first electrodes 1754 and 1755, a second insulating film1771, and second electrodes 1756 and 1757. The semiconductor film 1753has a first concentration one conductivity type impurity region 1758, asecond concentration one conductivity type impurity region 1759, andchannel formation regions 1760 and 1761.

[0339] The first electrodes 1754 and 1755 overlap the channel formationregions 1760 and 1761, respectively, with the first insulating film 1770sandwiched between the first electrodes and the channel formationregions. The second electrodes 1756 and 1757 overlap the channelformation regions 1760 and 1761, respectively, with the secondinsulating film 1771 sandwiched between the second electrodes and thechannel formation regions.

[0340] The p-channel TFT 1752 has a semiconductor film 1780, the firstinsulating film 1770, a first electrode 1782, the second insulating film1771, and a second electrode 1781. The semiconductor film 1780 has athird concentration one conductivity type impurity region 1783 and achannel formation region 1784.

[0341] The first electrode 1782 overlaps the channel formation region1784 with the first insulating film 1770 sandwiched therebetween. Thesecond electrode 1781 overlaps the channel formation region with thesecond insulating film 1771 sandwiched therebetween.

[0342] The first electrode 1782 and the second electrode 1781 areelectrically connected to each other through a wiring 1790.

[0343] A laser irradiation method of the present invention can be usedin formation of the semiconductor films 1753 and 1780, crystallization,activation, and other steps where laser annealing is used.

[0344] In this embodiment, a constant voltage is applied to the firstelectrode of the TFT used as a switching element (here, the n-channelTFT 1751). By applying a constant voltage 10 to the first electrode,fluctuation in threshold can be reduced and OFF current can be loweredcompared to the case where the TFT has only one electrode.

[0345] In the TFT (the p-channel TFT 1752 in this embodiment) where alarger current flows compared to the TFT used as a switching element,the first electrode and the second electrode are electrically connectedto each other. By applying the same voltage to the first electrode andthe second electrode, the depletion layer spreads quickly as though thesemiconductor film is actually reduced in thickness. Therefore thesub-threshold coefficient can be reduced and ON current can beincreased. Accordingly, when used in a driving circuit, the TFTstructured as this can lower the drive voltage. An increase in ONcurrent leads to reduction in size (channel width, in particular) of theTFT. As a result, the integration density can be improved.

[0346]FIG. 32 shows production flow for manufacturing the light emittingdevice of this embodiment. First, a semiconductor device is designedusing CAD. Specifically, a mask for an island is designed first and thena mask for a sub-island that includes one or more of such islands isdesigned. Then the designed pattern information of a sub-island isinputted to a computer of laser irradiation apparatus.

[0347] From the sub-island pattern information inputted, the computercalculates a width W_(S) of each sub-island in the directionperpendicular to the scanning direction. Based on the width W_(S) ofeach sub-island, a slit width W_(BW) in the direction perpendicular tothe scanning direction is set. The laser light scanning path isdetermined from the slit width W_(BW) with the position of a marker asthe reference.

[0348] During this, a first gate electrode is formed in accordance withthe marker formed on a substrate. Alternatively, the first gateelectrode and the marker may be formed at the same time. Then a firstinsulating film is formed so as to cover the first gate electrode and asemiconductor film is formed so as to come into contact with the firstinsulating film. The semiconductor film is patterned using the mask fora sub-island to form a sub-island. The substrate on which the sub-islandis formed is set on a stage of the laser irradiation apparatus.

[0349] With the marker as the reference, laser light runs along the setscanning path targeting the sub-island to crystallize the sub-island.

[0350] Thereafter, the sub-island having its crystallinity enhanced bythe laser light irradiation is patterned to form an island.Subsequently, a process of manufacturing a TFT from the island follows.Although specifics of the TFT manufacturing process are varied dependingon the TFT form, a typical process starts with forming an impurityregion in the island. Then laser irradiation follows and a secondinsulating film and a second electrode are sequentially formed so as tocover the island. An impurity region is formed in the island. Aninterlayer insulating film is then formed so as to cover the secondinsulating film and the second electrode. A contact hole is formed inthe interlayer insulating film to partially expose the impurity region.A wiring is then formed on the interlayer insulating film to reach theimpurity region through the contact hole.

[0351] This embodiment can be combined with any one of Embodiments 1through 8.

[0352] Embodiment 10

[0353] This embodiment describes an example in which a driving circuit(a signal line driving circuit or a scanning line driving circuit) isformed by using a laser irradiation method of the present invention andis mounted to a pixel portion formed from an amorphous semiconductorfilm using TAB, COG, or the like.

[0354]FIG. 40A shows an example of mounting a driving circuit to a TABtape so that a pixel portion is connected by the TAB tape to a printedsubstrate on which an external controller and others are formed. A pixelportion 5001 is formed on a glass substrate 5000, and is connectedthrough a TAB tape 5005 to a driving circuit 5002 that is manufacturedby a laser irradiation method of the present invention. The drivingcircuit 5002 is connected through the TAB tape 5005 to a printedsubstrate 5003. The printed substrate 5003 has a terminal 5004 forconnecting the substrate to an external interface.

[0355]FIG. 40B shows an example of mounting a driving circuit and apixel portion by COG. A pixel portion 5101 is formed on a glasssubstrate 5100, and a driving circuit 5102 manufactured by a laserirradiation method of the present invention is mounted to the glasssubstrate. The substrate 5100 has a terminal 5104 for connecting thesubstrate to an external interface.

[0356] As described, a TFT manufactured by a laser irradiation method ofthe present invention is improved in crystallinity of its channelformation region and therefore can operate at high speed. The TFT istherefore suitable for constituting a driving circuit which is requiredto operate at higher speed than a pixel portion. If the pixel portionand the driving circuit are manufactured separately, the yield isincreased.

[0357] This embodiment can be combined with any one of Embodiments 1through 9.

[0358] Embodiment 11

[0359] This embodiment describes a method of manufacturing a TFT using alaser irradiation method of the present invention.

[0360] First, as shown in FIG. 34A, an amorphous semiconductor film isformed on an insulating surface and etched to form island-likesemiconductor films 6001 and 6002. FIG. 34G is a top view of FIG. 34A,and a sectional view taken along the line A-A′ corresponds to FIG. 34A.Next, as shown in FIG. 34B, an amorphous semiconductor film 6003 isformed so as to cover the island-like semiconductor films 6001 and 6002.FIG. 34H is a top view of FIG. 34B, and a sectional view taken along theline A-A′ corresponds to FIG. 34B.

[0361] The amorphous semiconductor film 6003 is then patterned as shownin FIG. 34C to form a sub-island 6004 that covers the island-likesemiconductor layers 6001 and 6002. FIG. 34I is a top view of FIG. 34C,and a sectional view taken along the line A-A′ corresponds to FIG. 34C.Next, the island-like semiconductor layers 6001 and 6002 and thesub-island 6004 are selectively irradiated with laser light as shown inFIG. 34D to form island-like semiconductor films 6005 and 6006 andsub-island 6007 with improved crystallinity. The borders between theisland-like semiconductor films 6005 and 6006 and sub-island 6007 withimproved crystallinity may not be clear depending on laser lightirradiation conditions. Here, they are distinguished from one anotherbut may be deemed as one sub-island. FIG. 34J is a top view of FIG. 34D,and a sectional view taken along the line A-A′ corresponds to FIG. 34D.

[0362] The sub-island 6007 with improved crystallinity is then patternedas shown in FIG. 34E to form an island 6008. FIG. 34K is a top view ofFIG. 34E, and a sectional view taken along the line A-A′ corresponds toFIG. 34E. A TFT is formed from the island 6008 as shown in FIG. 34F.Specifics of the TFT manufacturing process that follows are varieddepending on the TFT form. However, a typical process includes forming agate insulating film 6009 so as to come into contact with the island6008, forming a gate electrode 6010 on the gate insulating film, formingimpurity regions 6011 and 6012 and a channel formation region 6013 inthe island 6008, forming an interlayer insulating film 6014 to cover thegate insulating film 6009, the gate electrode 6010, and the island 6008,and forming wirings 6015 and 6016 on the interlayer insulating film 6014to connect the wirings to the impurity regions 6011 and 6012. FIG. 34Lis a top view of FIG. 34F, and a sectional view taken along the lineA-A′ corresponds to FIG. 34F.

[0363] The impurity regions 6011 and 6012 are composed of theisland-like semiconductor films 6005 and 6006 and a part of the island6008. Therefore the impurity regions 6011 and 6012 are thicker than thechannel formation region 6013 and the resistance of the impurity regionscan be lowered.

[0364] Although the sub-island is crystallized by laser light alone inFIGS. 34A to 34L, a step of crystallizing the semiconductor films usinga catalytic element may be added.

[0365] A method of forming an island using a catalytic element and laserlight both is described with reference to FIGS. 35A to 35G. In using acatalytic element, it is desirable to employ techniques disclosed in JP07-130652 A and JP 08-78329 A.

[0366] First, as shown in FIG. 35A, an amorphous semiconductor film isformed on an insulating surface and etched to form island-likesemiconductor films 6101 and 6102. Next, as shown in FIG. 35B, anamorphous semiconductor film 6103 is formed so as to cover theisland-like semiconductor films 6101 and 6102. As shown in FIG. 35C, anickel acetate solution containing 10 ppm of nickel by weight is appliedto the amorphous semiconductor film 6103 to form a nickel-containinglayer. After a dehydrogenation step at 500° C. for an hour, theamorphous semiconductor film is subjected to heat treatment at 500 to650° C. for 4 to 12 hours, for example, at 550° C. for 8 hours, forcrystallization to obtain island-like semiconductor films 6104 and 6105and semiconductor film 6106 with improved crystallinity. Examples ofother employable catalytic elements than nickel (Ni) include elementssuch as germanium (Ge), iron (Fe), palladium (Pd), tin (Sn), lead (Pb),cobalt (Co), platinum (Pt), copper (Cu), and gold (Au).

[0367] The semiconductor film 6106 and the island-like semiconductorfilms 6104 and 6105 contain the catalytic element, which is removed fromthe crystalline semiconductor films by gettering. For gettering, atechnique disclosed in JP 10-135468 A or JP 10-135469 A can be employed.As shown in FIG. 35D, portions of the semiconductor film 6106 withimproved crystallinity, regions 6107 and 6108, are doped with phosphorusand then subjected to heat treatment in a nitrogen atmosphere at 550 to800° C. for 5 to 24 hours, for example, at 600° C. for 12 hours. Thiscauses the phosphorus-doped regions 6107 and 6108 to act as getteringsites, so that nickel present in the semiconductor film 6106 and in theisland-like semiconductor films 6104 and 6105 is moved to thephosphorus-doped regions and segregated. After that, thephosphorus-doped regions of the polycrystalline semiconductor films areremoved by patterning to obtain an island in which the catalytic elementconcentration is reduced down to 1×10¹⁷ atoms/cm³ or less, preferably,1×10¹⁶ atoms/cm³ or less.

[0368] Next, the island-like semiconductor films that have receivedgettering are patterned as shown in FIG. 35E to form a sub-island 6109.The sub-island 6109 is selectively irradiated with laser light as shownin FIG. 35F to improve its crystallinity even more. The sub-island 6109with improved crystallinity is then patterned to form an island 6110.

[0369] The description given next with reference to FIGS. 36A to 36G isabout another method of forming an island using a catalytic element andlaser light both.

[0370] First, as shown in FIG. 36A, an amorphous semiconductor film isformed on an insulating surface and etched to form island-likesemiconductor films 6201 and 6202. Next, as shown in FIG. 36B, anamorphous semiconductor film 6203 is formed so as to cover theisland-like semiconductor films 6201 and 6202. The amorphoussemiconductor film 6203 is patterned as shown in FIG. 36C to form asub-island. A nickel acetate solution containing 10 ppm of nickel byweight is applied to the sub-island to form a nickel-containing layer.The sub-island is then irradiated with laser light and heated to formisland-like semiconductor films 6204 and 6205 and sub-island 6206 withimproved crystallinity. Examples of other employable catalytic elementsthan nickel (Ni) include elements such as germanium (Ge), iron (Fe),palladium (Pd), tin (Sn), lead (Pb), cobalt (Co), platinum (Pt), copper(Cu), and gold (Au).

[0371] The sub-island 6206 and the island-like semiconductor films 6204and 6205 contain the catalytic element, which is removed from thecrystalline semiconductor films by gettering.

[0372] As shown in FIG. 36D, a barrier layer 6207 mainly containingsilicon is formed on the sub-island 6206. A very thin film can serve asthe barrier layer 6207 and it may be a natural oxide film.Alternatively, the barrier layer may be an oxide film oxidized bygenerating ozone through ultraviolet irradiation in an atmospherecontaining oxygen. It is also possible to use as the barrier layer 6207an oxide film oxidized by an ozone-containing solution that is used insurface treatment called hydro-washing for removing carbon, i.e.,organic substances. The barrier layer 6207 mainly serves as an etchingstopper. Formation of the barrier layer 6207 may be followed by channeldoping and then irradiation with intense light for activation.

[0373] Next, a second semiconductor film 6208 is formed on the barrierlayer 6207. The second semiconductor film 6208 may be a semiconductorfilm having an amorphous structure or a semiconductor film having acrystalline structure. The thickness of the second semiconductor film6208 is set to 5 to 50 nm, preferably, 10 to 20 nm. It is desirable forthe second semiconductor film 6208 to contain oxygen (in a concentrationof 5×10¹⁸/cm³ or more, preferably 1×10¹⁹/cm³ or more according to SIMS)in order to improve the gettering efficiency.

[0374] Formed on the second semiconductor film 6208 is a thirdsemiconductor film (gettering site) 6209 containing a rare gas element.The third semiconductor film 6209 may be a semiconductor film with anamorphous structure which is formed by plasma CVD, reduced pressurethermal CVD, or sputtering, or may be a semiconductor film having acrystalline structure. The third semiconductor film may contain a raregas element when it is being formed into a film. Alternatively, asemiconductor film which does not contain a rare gas element at the timeof its formation may be doped with a rare gas element and used as thethird semiconductor film. The third semiconductor film 6209 in thisembodiment has contained a rare gas element since its formation and isfurther doped with a rare gas element by selective doping. (FIG. 36E)The second semiconductor film and the third semiconductor film may beformed in succession without exposing them to the air. The sum of thethicknesses of the second semiconductor film and third semiconductorfilm is set to 30 to 200 nm, for example, 50 nm.

[0375] In this embodiment, the third semiconductor film (gettering site)6209 is distanced from the sub-island 6206 and the island-likesemiconductor films 6204 and 6205 by the second semiconductor film 6208.During gettering, a metal or other impurities present in the sub-island6206 and in the island-like semiconductor films 6204 and 6205 tend togather near the border of the gettering site. Therefore, the border ofthe gettering site is desirably distanced from the sub-island 6206 andthe island-like semiconductor films 6204 and 6205 by the secondsemiconductor film 6208 as in this embodiment to improve the getteringefficiency. In addition, the second semiconductor film 6208 has aneffect of blocking impurity elements that are contained in the getteringsite to prevent them from diffusing and reaching the interface of thesub-island 6206 during gettering. Another effect of the secondsemiconductor film 6208 is protection of the sub-island 6206 againstdamage by doping of a rare gas element.

[0376] Next, gettering is carried out. Gettering is achieved by heattreatment in a nitrogen atmosphere at 450 to 800° C. for 1 to 24 hours,for example, at 550° C. for 14 hours. The heat treatment may be replacedby irradiation with intense light. Alternatively, heat treatment plusintense light irradiation may be employed. Another option is to heat thesubstrate by spraying heated gas. In this case, it is sufficient if thesubstrate is heated at 600 to 800° C., desirably 650 to 750° C., for 1to 60 minutes and the gettering time can be shortened. Through thegettering, the impurity elements move in the direction indicated by thearrow in FIG. 36F. As a result, the impurity elements contained in thesub-island 6206 and island-like semiconductor films 6204 and 6205 whichare covered with the barrier layer 6207 are removed, or theconcentration of the impurity elements in the sub-island and theisland-like semiconductor films is lowered. Here, all of the impurityelements are moved into the third semiconductor film 6209 whilepreventing the impurity elements from segregating in the sub-island 6206and the island-like semiconductor films 6204 and 6205. The sub-island6206 and the island-like semiconductor films 6204 and 6205 shouldreceive thorough gettering so that almost none of the impurity elementsare left in the sub-island 6206 and the island-like semiconductor films6204 and 6205, in other words, so that the impurity elementconcentration in the films becomes 1×10¹⁸/cm³ or less, desirably1×10¹⁷/cm³ or less.

[0377] Next, the barrier layer 6207 is used as an etching stopper toselectively remove semiconductor films 6208 and 6209 alone. Then thesub-island 6206 is patterned by a known patterning technique to form anisland 6210 with a desired shape. (FIG. 36G)

[0378] This embodiment can be combined with any one of Embodiments 1through 10.

[0379] Embodiment 12

[0380] This embodiment gives a description on the structure of a TFTformed by using a laser irradiation method of the present invention.

[0381] A TFT shown in FIG. 37A has an active layer that includes achannel formation region 7001, first impurity regions 7002, and secondimpurity regions 7003. The first impurity regions 7002 sandwich thechannel formation region 7001. The second impurity regions 7003 areformed between the first impurity regions 7002 and the channel formationregion 7001. The TFT also has a gate insulating film 7004 that is incontact with the active layer and a gate electrode 7005 that is formedon the gate insulating film. Side walls 7006 are formed by the gateelectrode and in contact with the side faces of the gate electrode.

[0382] The side walls 7006 overlap the second impurity regions 7003 withthe gate insulating film 7004 sandwiched between the side walls and thesecond impurity regions. The side walls 7006 may be conductive orinsulative. When the side walls 7006 are conductive, the side walls 7006may constitute a part of the gate electrode.

[0383] A TFT shown in FIG. 37B has an active layer that includes achannel formation region 7101, first impurity regions 7102, and secondimpurity regions 7103. The first impurity regions 7102 sandwich thechannel formation region 7101. The second impurity regions 7103 areformed between the first impurity regions 7102 and the channel formationregion 7101. The TFT also has a gate insulating film 7104 that is incontact with the active layer and a gate electrode that is formed on thegate insulating film. The gate electrode is a laminate of two conductivefilms 7105 and 7106. Side walls 7107 are formed on the conductive layer7105 and by the conductive layer 7106 so that the side walls are incontact with the top face of 7105 and the side faces of 7106.

[0384] The side walls 7107 may be conductive or insulative. When theside walls 7107 are conductive, the side walls 7107 may constitute apart of the gate electrode.

[0385] A TFT shown in FIG. 37C has an active layer that includes achannel formation region 7201, first impurity regions 7202, and secondimpurity regions 7203. The first impurity regions 7202 sandwich thechannel formation region 7201. The second impurity regions 7203 areformed between the first impurity regions 7202 and the channel formationregion 7201. The TFT also has a gate insulating film 7204 that is incontact with the active layer. A conductive film 7205 is formed on thegate insulating film. A conductive film 7206 covers the top and sidefaces of the conductive film 7205. Side walls 7207 are formed by theconductive film 7206 and in contact with the side faces of theconductive film 7206. The conductive films 7205 and 7206 function as agate electrode.

[0386] The side walls 7207 may be conductive or insulative. When theside walls 7207 are conductive, the side walls 7207 may constitute apart of the gate electrode.

[0387] This embodiment can be combined with any one of Embodiments 1through 11.

[0388] Embodiment 13

[0389] The structure of a pixel in a light emitting device of thepresent invention will be described with reference to FIG. 41.

[0390] In FIG. 41, a base film 6001 is formed on a substrate 6000 and atransistor 6002 is formed on the base film 6001. The transistor 6002 hasan active layer 6003, a gate electrode 6005, and a gate insulating film6004, which is sandwiched between the active layer 6003 and the gateelectrode 6005.

[0391] The active layer 6003 is preferably a polycrystallinesemiconductor film, and the polycrystalline semiconductor film can beformed by a laser irradiation apparatus of the present invention.

[0392] The active layer may be formed of silicon germanium other thansilicon. When silicon germanium is employed, the germanium concentrationis preferably about 0.01 to 4.5 atomic %. Silicon doped with carbonnitride may also be used.

[0393] The gate insulating film 6004 can be formed from silicon oxide,silicon nitride, or silicon oxynitride. A silicon oxide film, a siliconnitride film, and a silicon oxynitride film may be layered to form thegate insulating film. For example, a SiN film laid on a SiO₂ film can beused. A silicon oxide film is formed by plasma CVD in which TEOS(tetraethyl orthosilicate) and O₂ are mixed, the reaction pressure isset to 40 Pa, the substrate temperature is set to 300 to 400° C., andthe high frequency (13.56 MHz) power density is set to 0.5 to 0.8 W/cm²for electric discharge. The thus formed silicon oxide film can provideexcellent characteristics as a gate insulating film if it subsequentlyreceives thermal annealing at 400 to 500° C. The gate insulating filmmay also be formed of aluminum nitride. Aluminum nitride has relativelyhigh heat conductivity and is capable of diffusing heat generated in theTFT effectively. A laminate obtained by laying an aluminum nitride filmon a silicon oxide film, a silicon oxynitride film, or the like whichdoes not contain aluminum may also be used as the gate insulating film.It is also possible to employ a SiO₂ film formed by RF sputtering withSi as the target for the gate insulating film.

[0394] The gate electrode 6005 is formed of an element selected from thegroup consisting of Ta, W, Ti, Mo, Al, and Cu, or an alloy or compoundmainly containing the above elements. Alternatively, the gate electrodemay be a semiconductor film, typically polycrystalline silicon film,doped with phosphorus or other impurity elements. Instead of asingle-layer conductive film, a laminate of plural conductive films maybe used as the gate electrode.

[0395] The following are examples of a preferred combination ofconductive films: a combination of a tantalum nitride (TaN) film as thefirst conductive film and a W film as the second conductive film, acombination of a tantalum nitride (TaN) film as the first conductivefilm and a Ti film as the second conductive film, a combination of atantalum nitride (TaN) film as the first conductive film and an Al filmas the second conductive film, and a combination of a tantalum nitride(TaN) film as the first conductive film and a Cu film as the secondconductive film. Alternatively, the first conductive film and the secondconductive film may be semiconductor films, typically polycrystallinesilicon films, doped with phosphorus or other impurities, or may beAg—Pd—Cu alloy films.

[0396] The gate electrode is not limited to the two-layer structure. Forexample, a three-layer structure consisting of a tungsten film,aluminum-silicon alloy (Al—Si) film, and titanium nitride film layeredin this order may be employed. When the three-layer structure isemployed, the tungsten film may be replaced by a tungsten nitride film,the aluminum-silicon alloy (Al—Si) film may be replaced by analuminum-titanium alloy (Al—Ti) film, and the titanium nitride film maybe replaced by a titanium film.

[0397] It is important to select the optimum etching method and etchantfor the conductive film material employed.

[0398] The transistor 6002 is covered with a first interlayer insulatingfilm 6006. A second interlayer insulating film 6007 and a thirdinterlayer insulating film 6008 are layered on the first interlayerinsulating film 6006.

[0399] The first interlayer insulating film 6006 is a single layer orlaminate of a silicon oxide film, silicon nitride film, and siliconoxynitride film formed by plasma CVD or sputtering. A laminate obtainedby laying a silicon oxynitride film in which oxygen is higher in molefraction than nitrogen on top of a silicon oxynitride film in whichnitrogen is higher in mole fraction than oxygen may also be used as thefirst interlayer insulating film 6006.

[0400] If thermal processing (heat treatment at 300 to 550° C. for 1 to12 hours) is conducted after the first interlayer insulating film 6006is formed, dangling bonds of semiconductors in the active layer 6003 canbe terminated (hydrogenated) by hydrogen contained in the firstinterlayer insulating film 6006.

[0401] The second interlayer insulating film 6007 can be formed ofnon-photosensitive acrylic.

[0402] Used as the third interlayer insulating film 6008 should be afilm that does not easily transmit moisture, oxygen, and othersubstances that accelerate degradation of a light emitting elementcompared to the other insulating films. Typically, a DLC film, a carbonnitride film, a silicon nitride film formed by RF sputtering, or thelike is desirably used as the third interlayer insulating film.

[0403] In FIG. 41, denoted by 6010 is an anode, 6011, an electric fieldlight emitting layer, and 6012, a cathode. An area where the anode 6010,the electric field light emitting layer 6011, and the cathode 6012overlap corresponds to a light emitting element 6013. The transistor6002 is a driving transistor for controlling a current supplied to thelight emitting element 6013, and is connected to the light emittingelement 6013 directly or in series through another circuit element.

[0404] The electric field light emitting layer 6011 may be a lightemitting layer alone or a laminate of plural layers including a lightemitting layer.

[0405] The anode 6010 is formed on the third interlayer insulating film6008. Also formed on the third interlayer insulating film 6008 is anorganic resin film 6014, which is used as a partition wall. The organicresin film 6014 has an opening 6015 where the anode 6010, the electricfield light emitting layer 6011, and the cathode 6012 overlap to formthe light emitting element 6013.

[0406] A protective film 6016 is formed on the organic resin film 6014and the cathode 6012. Used as the protective film 6016 is, similar tothe third interlayer insulating film 6008, a film that does not easilytransmit moisture, oxygen, and other substances that acceleratedegradation of a light emitting element compared to the other insulatingfilms. Typically, a DLC film, a carbon nitride film, a silicon nitridefilm formed by RF sputtering, or the like is used as the protectivefilm. It is also possible to use as the protective film a laminate ofthe above-described film that does not easily transmit moisture, oxygen,and other substances and a film that transmits moisture, oxygen, andother substances easily compared to the former film.

[0407] Before the electric field light emitting layer 6011 is formed,the organic resin film 6014 is heated in a vacuum atmosphere to removeadsorbed moisture, oxygen, and the like. Specifically, heat treatment isconducted in a vacuum atmosphere at 100 to 200° C. for about 0.5 to 1hour. The pressure is set to desirably 3×10⁻⁷ Torr or lower, ifpossible, 3×10⁻⁸ Torr or lower is the best. When the electric fieldlight emitting layer is formed, after the heat treatment of the organicresin film in a vacuum atmosphere, the vacuum atmosphere is maintaineduntil the last moment before the electric field light emitting layer isformed. This enhances the reliability even more.

[0408] The end of the organic resin film 6014 in the opening 6015 isdesirably rounded in order to prevent the end from poking a hole in theelectric field light emitting layer 6011 that is formed on the organicresin film 6014 and partially overlaps the organic resin film. To bespecific, the radius of curvature of the curved organic resin film insection in the opening is desirably about 0.2 to 2 μm.

[0409] The above structure gives the electric field light emitting layerand cathode formed later an excellent coverage and can avoid a situationwhere a hole is formed in the electric field light emitting layer 6011and causes short circuit of the anode 6011 and the cathode 6012. Adefect called shrink which refers to reduction of the light emittingregion can be reduced by relieving the stress of the electric fieldlight emitting layer 6011, and the reliability is thus enhanced.

[0410] In the example shown in FIG. 41, a positive photosensitiveacrylic resin is used for the organic resin film 6014. Photosensitiveorganic resins are classified into a positive type and a negative type.A-part of a resin that is exposed to an energy beam such as light,electron, and ion is removed if the resin is the positive type and isleft if the resin is the negative type. A negative type organic resinfilm too can be used in the present invention. Also, the organic resinfilm 6014 may be formed from photosensitive polyimide.

[0411] When a negative acrylic resin is used to form the organic resinfilm 6014, the end of the organic resin film in the opening 6015 isshaped like the letter S in section. The radius of curvature thereof atthe upper edge and lower edge of the opening is desirably 0.2 to 2 μm.

[0412] The anode 6010 may be formed from a transparent conductive film.An ITO film as well as a transparent conductive film obtained by mixing2 to 20% of zinc oxide (ZnO) with indium oxide can be employed. In FIG.41, ITO is used for the anode 6010. The anode 6010 may be polished byCMP or a porous polyvinyl alcohol-based substance (Bellclean washing) inorder to level its surface. The surface of the anode 6010 which hasreceived polishing by CMP may be subjected to ultraviolet irradiation oroxygen plasma treatment.

[0413] The cathode 6012 can be formed from other known material as longas it is a conductive film having a small work function. For instance,Ca, Al, CaF, MgAg, AlLi, and the like are desirable.

[0414] In the structure shown in FIG. 41, light from the light emittingelement is emitted toward the substrate 6000 side. However, the lightemitting element may be structured such that emitted light travels inthe direction opposite to the substrate.

[0415] In FIG. 41, the transistor 6002 is connected to the anode 6010 ofthe light emitting element. However, the present invention is notlimited thereto and the transistor 6002 may be connected to the cathode6001 of the light emitting element. In this case, the cathode is formedon the third interlayer insulating film 6008 from TiN or the like.

[0416] In practice, it is preferable to package (seal) the device thathas reached the stage of FIG. 41 with a protective film which is highlyairtight and which allows little gas to leak (a laminate film, aUV-curable resin film, or the like) or a light-transmissive cover memberin order to avoid exposure to the outside air. In packaging the device,the interior of the cover member may be set to inert atmosphere or ahygroscopic material (such as barium oxide) may be put inside in orderto improve the reliability of the device.

[0417] The present invention is not limited to the manufacturing methoddescribed above, and the device can be manufactured using a knownmethod. This embodiment can be combined freely with Embodiments 1through 13.

[0418] The present invention runs laser light so as to obtain at leastthe minimum degree of crystallization of a portion that has to becrystallized, instead of irradiating the entire semiconductor film withlaser light. With the above structure, time for laser irradiation ofportions that are removed by patterning after crystallization of thesemiconductor film can be saved to greatly shorten the processing timeper substrate.

[0419] Furthermore, the crystallinity of a semiconductor film can beenhanced more efficiently by overlapping plural laser beams tocompensate one another's low energy density portions compared to thecase where laser beams are not overlapped and a single laser beam isused.

[0420] Although the description given in the present invention is aboutthe case where laser light emitted from plural laser oscillationapparatuses are synthesized, the present invention is not particularlylimited thereto. The present invention may use only one laseroscillation apparatus if it has relatively high output energy and iscapable of providing a desired energy density without reducing the areaof its beam spot. In this case also, the use of a slit makes it possibleto block low energy density portions of laser light and to control thebeam spot width in accordance with pattern information.

What is claimed is:
 1. A method of manufacturing a semiconductor device,comprising: forming a semiconductor film over a substrate; patterningthe semiconductor film to form a sub-island and a marker; determining,from pattern information of the sub-island, a width in a directionperpendicular to a scanning direction of a laser beam spot and ascanning path of the beam spot so as to include the sub-island;controlling the width in the direction perpendicular to the scanningdirection of the beam spot by using a slit; running the beam spot alongthe scanning path with the marker as the reference to enhancecrystallinity of the sub-island; and patterning the sub-island withenhanced crystallinity to form an island.
 2. A method of manufacturing asemiconductor device, comprising: forming a semiconductor film over asubstrate; patterning the semiconductor film to form a sub-island usinga mask; detecting pattern information of the sub-island using a CCD;grasping a position of the substrate by checking pattern information ofthe mask against the pattern information of the sub-island; determining,from the pattern information of the sub-island, a width in a directionperpendicular to a scanning direction of a laser beam spot and ascanning path of the beam spot so as to include the sub-island;controlling the width in the direction perpendicular to the scanningdirection of the beam spot by using a slit; running the beam spot alongthe scanning path with the marker as the reference to enhancecrystallinity of the sub-island; and patterning the sub-island withenhanced crystallinity to form an island.
 3. A method of manufacturing asemiconductor device, comprising: forming a semiconductor film over asubstrate; patterning the semiconductor film to form a sub-island and amarker; determining, from pattern information of the sub-island, a widthin a direction perpendicular to a scanning direction of a laser beamspot and a scanning path of the beam spot so as to include thesub-island; controlling the width in the direction perpendicular to thescanning direction of the beam spot by using a slit; running the beamspot along the scanning path with the marker as the reference to enhancecrystallinity of the sub-island; and patterning the sub-island withenhanced crystallinity to form an island, wherein, when the beam spotreaches the sub-island during running the beam spot, one point of thebeam spot comes into contact with the sub-island.
 4. A method ofmanufacturing a semiconductor device, comprising: forming asemiconductor film over a substrate; patterning the semiconductor filmto form a sub-island using a mask; detecting pattern information of thesub-island using a CCD; grasping a position of the substrate by checkingpattern information of the mask against the pattern information of thesub-island; determining, from the pattern information of the sub-island,a width in a direction perpendicular to a scanning direction of a laserbeam spot and a scanning path of the beam spot so as to include thesub-island; controlling the width in the direction perpendicular to thescanning direction of the beam spot by using a slit; running the beamspot along the scanning path with the marker as the reference to enhancecrystallinity of the sub-island; and patterning the sub-island withenhanced crystallinity to form an island, wherein, when the beam spotreaches the sub-island during running the beam spot, one point of thebeam spot comes into contact with the sub-island.
 5. A method ofmanufacturing a semiconductor device, comprising: forming asemiconductor film over a substrate; patterning the semiconductor filmto form a sub-island and a marker; determining, from pattern informationof the sub-island with the marker as the reference, a specific region onthe substrate that is to be irradiated with laser light, the regionincluding the sub-island; using an optical system to partially overlapbeam spots of plural laser lights that are outputted from plural laseroscillation apparatuses to form one beam spot; using a slit to reducethe width in the direction perpendicular to the scanning direction ofthe beam spot formed; running the beam spot with the reduced width overthe specific region to enhance crystallinity of the sub-island; andpatterning the sub-island with enhanced crystallinity to form an island.6. A method of manufacturing a semiconductor device, comprising: forminga semiconductor film over a substrate; patterning the semiconductor filmto form a sub-island and a marker; determining, from pattern informationof the sub-island with the marker as the reference, a specific region onthe substrate that is to be irradiated with laser light, the regionincluding the sub-island; using an optical system to partially overlapbeam spots of plural laser lights that are outputted from plural laseroscillation apparatuses so that centers draw straight lines to form onebeam spot; using a slit to reduce the width in the directionperpendicular to the scanning direction of the beam spot formed; runningthe beam spot with the reduced width over the specific region to enhancecrystallinity of the sub-island; and patterning the sub-island withenhanced crystallinity to form an island.
 7. A method of manufacturing asemiconductor device according to claim 5, wherein the straight linesthe centers draw are at angles of 10° or larger and 80° or less with thedirection in which the substrate moves.
 8. A method of manufacturing asemiconductor device according to claim 6, wherein the straight linesthe centers draw are at angles of 10° or larger and 80° or less with thedirection in which the substrate moves.
 9. A method of manufacturing asemiconductor device according to claim 5, wherein the straight linesthe centers draw are almost at right angles with the direction thesubstrate moves.
 10. A method of manufacturing a semiconductor deviceaccording to claim 6, wherein the straight lines the centers draw arealmost at right angles with the direction the substrate moves.
 11. Amethod of manufacturing a semiconductor device according to claim 5,wherein the beam spot formed has a linear shape.
 12. A method ofmanufacturing a semiconductor device according to claim 6, wherein thebeam spot formed has a linear shape.
 13. A method of manufacturing asemiconductor device according to claim 1, wherein laser lightirradiation takes place in a reduced pressure atmosphere or inert gasatmosphere.
 14. A method of manufacturing a semiconductor deviceaccording to claim 2, wherein laser light irradiation takes place in areduced pressure atmosphere or inert gas atmosphere.
 15. A method ofmanufacturing a semiconductor device according to claim 3, wherein laserlight irradiation takes place in a reduced pressure atmosphere or inertgas atmosphere.
 16. A method of manufacturing a semiconductor deviceaccording to claim 4, wherein laser light irradiation takes place in areduced pressure atmosphere or inert gas atmosphere.
 17. A method ofmanufacturing a semiconductor device according to claim 5, wherein laserlight irradiation takes place in a reduced pressure atmosphere or inertgas atmosphere.
 18. A method of manufacturing a semiconductor deviceaccording to claim 6, wherein laser light irradiation takes place in areduced pressure atmosphere or inert gas atmosphere.
 19. A method ofmanufacturing a semiconductor device according to claim 1, wherein thelaser light is outputted from one or more kinds of lasers selected fromthe group consisting of a YAG laser, a YVO₄ laser, a YLF laser, a YAlO₃laser, a glass laser, a ruby laser, an alexandrite laser, a Ti: sapphirelaser, and a Y₂O₃ laser.
 20. A method of manufacturing a semiconductordevice according to claim 2, wherein the laser light is outputted fromone or more kinds of lasers selected from the group consisting of a YAGlaser, a YVO₄ laser, a YLF laser, a YAlO₃ laser, a glass laser, a rubylaser, an alexandrite laser, a Ti: sapphire laser, and a Y₂O₃ laser. 21.A method of manufacturing a semiconductor device according to claim 3,wherein the laser light is outputted from one or more kinds of lasersselected from the group consisting of a YAG laser, a YVO₄ laser, a YLFlaser, a YAlO₃ laser, a glass laser, a ruby laser, an alexandrite laser,a Ti: sapphire laser, and a Y₂O₃ laser.
 22. A method of manufacturing asemiconductor device according to claim 4, wherein the laser light isoutputted from one or more kinds of lasers selected from the groupconsisting of a YAG laser, a YVO₄ laser, a YLF laser, a YAlO₃ laser, aglass laser, a ruby laser, an alexandrite laser, a Ti: sapphire laser,and a Y₂O₃ laser.
 23. A method of manufacturing a semiconductor deviceaccording to claim 5, wherein the laser light is outputted from one ormore kinds of lasers selected from the group consisting of a YAG laser,a YVO₄ laser, a YLF laser, a YAlO₃ laser, a glass laser, a ruby laser,an alexandrite laser, a Ti: sapphire laser, and a Y₂O₃ laser.
 24. Amethod of manufacturing a semiconductor device according to claim 6,wherein the laser light is outputted from one or more kinds of lasersselected from the group consisting of a YAG laser, a YVO₄ laser, a YLFlaser, a YAlO₃ laser, a glass laser, a ruby laser, an alexandrite laser,a Ti: sapphire laser, and a Y₂O₃ laser.
 25. A method of manufacturing asemiconductor device according to claim 1, wherein the laser light iscontinuous wave laser light.
 26. A method of manufacturing asemiconductor device according to claim 2, wherein the laser light isoutputted from one or more kinds of lasers selected from the groupconsisting of a YAG laser, a YVO₄ laser, a YLF laser, a YAlO₃ laser, aglass laser, a ruby laser, an alexandrite laser, a Ti: sapphire laser,and a Y₂O₃ laser.
 27. A method of manufacturing a semiconductor deviceaccording to claim 3, wherein the laser light is outputted from one ormore kinds of lasers selected from the group consisting of a YAG laser,a YVO₄ laser, a YLF laser, a YAlO₃ laser, a glass laser, a ruby laser,an alexandrite laser, a Ti: sapphire laser, and a Y₂O₃ laser.
 28. Amethod of manufacturing a semiconductor device according to claim 4,wherein the laser light is outputted from one or more kinds of lasersselected from the group consisting of a YAG laser, a YVO₄ laser, a YLFlaser, a YAlO₃ laser, a glass laser, a ruby laser, an alexandrite laser,a Ti: sapphire laser, and a Y₂O₃ laser.
 29. A method of manufacturing asemiconductor device according to claim 5, wherein the laser light isoutputted from one or more kinds of lasers selected from the groupconsisting of a YAG laser, a YVO₄ laser, a YLF laser, a YAlO₃ laser, aglass laser, a ruby laser, an alexandrite laser, a Ti: sapphire laser,and a Y₂O₃ laser.
 30. A method of manufacturing a semiconductor deviceaccording to claim 6, wherein the laser light is outputted from one ormore kinds of lasers selected from the group consisting of a YAG laser,a YVO₄ laser, a YLF laser, a YAlO₃ laser, a glass laser, a ruby laser,an alexandrite laser, a Ti: sapphire laser, and a Y₂O₃ laser.
 31. Amethod of manufacturing a semiconductor device according to claim 1,wherein the laser light is second harmonic.
 32. A method ofmanufacturing a semiconductor device according to claim 2, wherein thelaser light is second harmonic.
 33. A method of manufacturing asemiconductor device according to claim 3, wherein the laser light issecond harmonic.
 34. A method of manufacturing a semiconductor deviceaccording to claim 4, wherein the laser light is second harmonic.
 35. Amethod of manufacturing a semiconductor device according to claim 5,wherein the laser light is second harmonic.
 36. A method ofmanufacturing a semiconductor device according to claim 6, wherein thelaser light is second harmonic.
 37. A method of manufacturing asemiconductor device according to claim 5, wherein the number of thelaser oscillation apparatuses is equal to or more than 2 and equal to orless than
 8. 38. A method of manufacturing a semiconductor deviceaccording to claim 6, wherein the number of the laser oscillationapparatuses is equal to or more than 2 and equal to or less than
 8. 39.A method of manufacturing a semiconductor device according to claim 1,wherein the width of the slit is variable.
 40. A method of manufacturinga semiconductor device according to claim 2, wherein the width of theslit is variable.
 41. A method of manufacturing a semiconductor deviceaccording to claim 3, wherein the width of the slit is variable.
 42. Amethod of manufacturing a semiconductor device according to claim 4,wherein the width of the slit is variable.
 43. A method of manufacturinga semiconductor device according to claim 5, wherein the width of theslit is variable.
 44. A method of manufacturing a semiconductor deviceaccording to claim 6, wherein width of the slit is variable.
 45. A laserirradiation method comprising: determining, from pattern information ofa sub-island obtained by patterning a semiconductor film formed over asubstrate with a marker as the reference, a specific region on thesubstrate that is to be irradiated with laser light, the regionincluding the sub-island; using an optical system to partially overlapbeam spots of plural laser lights that are outputted from plural laseroscillation apparatuses to form one beam spot; using a slit to reduce awidth in a direction perpendicular to a scanning direction of the beamspot formed; running the beam spot with the reduced width over thespecific region to enhance crystallinity of the sub-island; andpatterning the sub-island with enhanced crystallinity to form an island.46. A laser irradiation method comprising: determining, from patterninformation of the sub-island obtained by patterning a semiconductorfilm formed over a substrate with the marker as the reference, aspecific region on the substrate that is to be irradiated with laserlight, the region including the sub-island; using an optical system topartially overlap beam spots of plural laser lights that are outputtedfrom plural laser oscillation apparatuses so that centers draw straightlines to form one beam spot; using a slit to reduce the width in thedirection perpendicular to the scanning direction of the beam spotformed; running the beam spot with the reduced width over the specificregion to enhance crystallinity of the sub-island; and patterning thesub-island with enhanced crystallinity to form an island.
 47. A laserirradiation method according to claim 44, wherein the straight lines thecenters draw are at angles of 10° or larger and 80° or less with thedirection in which the substrate moves.
 48. A laser irradiation methodaccording to claim 45, wherein the straight lines the centers draw areat angles of 10° or larger and 80° or less with the direction in whichthe substrate moves.
 49. A laser irradiation method according to claim44, wherein the straight lines the centers draw are almost at rightangles with the direction in which the substrate moves.
 50. A laserirradiation method according to claim 45, wherein the straight lines thecenters draw are almost at right angles with the direction in which thesubstrate moves.
 51. A laser irradiation method according to claim 44,wherein laser light irradiation takes place in a reduced pressureatmosphere or inert gas atmosphere.
 52. A laser irradiation methodaccording to claim 45, wherein laser light irradiation takes place in areduced pressure atmosphere or inert gas atmosphere.
 53. A laserirradiation method according to claim 44, wherein the laser light isoutputted from one or more kinds of lasers selected from the groupconsisting of a YAG laser, a YVO₄ laser, a YLF laser, a YAlO₃ laser, aglass laser, a ruby laser, an alexandrite laser, a Ti: sapphire laser,and a Y₂O₃ laser.
 54. A laser irradiation method according to claim 45,wherein the laser light is outputted from one or more kinds of lasersselected from the group consisting of a YAG laser, a YVO₄ laser, a YLFlaser, a YAlO₃ laser, a glass laser, a ruby laser, an alexandrite laser,a Ti: sapphire laser, and a Y₂O₃ laser.
 55. A laser irradiation methodaccording to claim 44, wherein the laser light is continuous wave laserlight.
 56. A laser irradiation method according to claim 45, wherein thelaser light is second harmonic.
 57. A laser irradiation method accordingto claim 44, wherein the number of the laser oscillation apparatuses isequal to or more than 2 and equal to or less than
 8. 58. A laserirradiation method according to claim 45, wherein the laser light isoutputted from one or more kinds of lasers selected from the groupconsisting of a YAG laser, a YVO₄ laser, a YLF laser, a YAlO₃ laser, aglass laser, a ruby laser, an alexandrite laser, a Ti: sapphire laser,and a Y₂O₃ laser.